Watched I'd heard (4)
I believe the answer is:
eyed
'watched' is the definition.
(I've seen this in another clue)
'i'd heard' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'id' sounds like 'EYED'.
(Other definitions for eyed that I've seen before include "Vegetable" , "Viewed" , "Watched, looked at" , "Watched with interest" , "Spotted" .)