Checks closely (4)
I believe the answer is:
vets
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">checks closely</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 vets that I've seen before include "Siegfried and Tristan Farnon, for example" , "Screens the animal doctors" , "Ex-servicemen and women, in short" , "Screens for the job perhaps" , "Investigates thoroughly to ensure suitability, for a job perhaps" .)