Lose a staring contest (5)
I believe the answer is:
blink
'lose a staring contest' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for blink that I've seen before include "viewing interruption" , "Bat (eyelid)" , "Brief moment (of hesitation?)" , "Shut eye briefly" , "Nictate" .)