Pakistan's chief river (5)
I believe the answer is:
indus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pakistan's chief river</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for indus that I've seen before include "Pakistani river" , "River rising in Tibet" , "River of India/Pakistan" , "River of Southern Asia" , "Main river of Pakistan" .)