Look at the cover - the pupil's cover (6)
I believe the answer is:
eyelid
'pupil's cover' is the definition.
(I've seen this in another clue)
'look at the cover' is the wordplay.
'look at' becomes 'eye' (I've seen this before).
'the cover' becomes 'lid' (lid is a kind of cover).
'eye'+'lid'='EYELID'
'the' is the link.
(Other definitions for eyelid that I've seen before include "One winks with it" , "It may be batted" , "Blinking membrane" , "Natural optic protector" , "Covering for 27 across" .)