Observe closely (7)
I believe the answer is:
eyeball
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">observe closely</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 eyeball that I've seen before include "Watch" , "one to one is an aggressive stance" , "" - to - " = in close confrontation" , "making us stare" , "Label ye (anag)" .)