Veteran soldier (3,5)
I believe the answer is:
old sweat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">veteran soldier</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for old sweat that I've seen before include "Veteran soldier" , "Very experienced chap" , "Veteran, one expected to 7" .)