Shrink as key wore out (5)
I believe the answer is:
cower
'shrink' is the definition.
(I've seen this before)
'key wore out' is the wordplay.
'key' becomes 'c' (I've seen this in other clues**).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'wore' is an anagram of 'ower'.
'c'+'ower'='COWER'
'as' acts as a link.
(Other definitions for cower that I've seen before include "Shrink back in fear" , "Cringe, crouch" , "Crouch in fear" , "Grovel in fear" , "Cringe in fear" .)