or
निरंजन
fonts

\documentclass{article}
\usepackage{fontspec}
\setmainfont[Script=Devanagari,Mapping=devanagarinumerals]{Shobhika}
\usepackage{soulutf8}
\setul{0.26cm}{0.5pt}

\begin{document}
\underline{अबकड} \underline{कू} \underline{क्लू} \underline{ट्टू}
\ul{abcd} \ul{अबकड} \ul{कू} \ul{क्लू} \ul{ट्टू}
\end{document}


This produces -

![Screenshot from 2020-02-12 20-31-56.png](/image?hash=3fcc53fdab9e1fb3c98c38e7af78f49e44360db4b1691d5b845ba4215fc20e2b)

How to resolve this?
Assuming you want all the underlines on the same height, here two possibilities

### ulem package


% !TeX TS-program = xelatex

\documentclass{article}
\usepackage{fontspec}
\setmainfont[Script=Devanagari,Mapping=devanagarinumerals]{Shobhika}

\usepackage[normalem]{ulem}
\newlength{\mydepth}

% insert character with heighest depth here
\settodepth{\mydepth}{क्लू}

\renewcommand{\ULthickness}{0.15ex}
\setlength{\ULdepth}{\dimexpr\mydepth+0.3ex\relax}

\begin{document}

\uline{अबकड} \uline{कू} \uline{क्लू} \uline{ट्टू}

\end{document}


![Screen Shot 2020-02-13 at 00.44.43.png](/image?hash=4fa6e596e2c0145a0cd8f73d507f251cf5abfcd9bb3ce7f403d4154db8b95f3c)

### classic underline


% !TeX TS-program = xelatex

\documentclass{article}
\usepackage{fontspec}
\setmainfont[Script=Devanagari,Mapping=devanagarinumerals]{Shobhika}

\newlength{\mydepth}
\newlength{\myheight}

% insert character with heighest depth here
\settodepth{\mydepth}{क्लू}
\settoheight{\myheight}{क्लू}

\newcommand{\fix}{\rule[-\mydepth]{0pt}{\dimexpr\mydepth+\myheight\relax}}
\let\oldunderline\underline
\renewcommand{\underline}[1]{\oldunderline{\fix #1}}

\begin{document}

\underline{अबकड} \underline{कू} \underline{क्लू} \underline{ट्टू}

\end{document}


![Screen Shot 2020-02-13 at 00.47.07.png](/image?hash=694cf275653794b981c0769210669d7fcf1edad89488673272cae74c08eda9ce)
You're welcome!
निरंजन
Thank you so much :) This works exactly as expected.
You can disable underlining in the bibliography with \usepackage[normalem]{ulem}
Don't worry about the number of pings. Unless you reply to my message or explicitly ping me by clicking on my avatar, I'm not pinged at all. (on the contrary, it would be good to ping me to make sure I see your messages)
I modified my answer to automatically include the fix
निरंजन
Basically I don't want ulem to affect my references at all. Sorry for so many pings.
निरंजन
MWE if you want -

\begin{filecontents}{abcd.bib}
@book{MWE,
title={Sample book title},
author={Anybody},
year={today},
publisher={\LaTeX}
}
\end{filecontents}
\documentclass{article}
\usepackage[backend=biber,style=apa]{biblatex}
\usepackage{ulem}
\newlength{\mydepth}
\settodepth{\mydepth}{\LaTeX}
\renewcommand{\ULthickness}{0.15ex}
\setlength{\ULdepth}{\dimexpr\mydepth+0.3ex\relax}

\begin{document}
\cite{MWE}
\printbibliography
\end{document}

निरंजन
After using package ulem titles of my references (obtained with biblatex with biber) automatically got underlined. I don't want that to happen, how to turn it off?
निरंजन
but this solution looks great! Thanks.
निरंजन
Can this be done without the \fix? I want minimal changes in the commands.
samcarter
![Screen Shot 2020-02-12 at 17.15.16.png](/image?hash=e942b00f110bbe51805e21d207095629e0f156211b7cd22b6a4fa9d8174ac5d4)
samcarter

% !TeX TS-program = xelatex

\documentclass{article}
\usepackage{fontspec}
\setmainfont[Script=Devanagari,Mapping=devanagarinumerals]{Shobhika}
\usepackage{soulutf8}

\newlength{\mydepth}
\newlength{\myheight}

% insert character with heighest depth here
\settodepth{\mydepth}{क्लू}
\settoheight{\myheight}{क्लू}

\newcommand{\fix}{\rule[-\mydepth]{0pt}{\dimexpr\mydepth+\myheight\relax}}

\begin{document}

\underline{\fix अबकड} \underline{\fix कू} \underline{\fix क्लू} \underline{\fix ट्टू}

\end{document}

samcarter
If they should all be on the same height, you could try something like
samcarter
Should all be on the same height or just below the characters?
samcarter
@निरंजन On which height do you want the line?