Part of blade, yet rotating in saw (4)
I believe the answer is:
eyed
'saw' is the definition.
(I've seen this in another clue)
'part of blade yet rotating' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'rotating' shows that the letters should be reversed in order.
'deye' is hidden within 'blade yet'.
'deye' reversed gives 'EYED'.
'in' is the link.
(Other definitions for eyed that I've seen before include "Saw" , "Watched warily" , "Watched, looked at" , "Looked at, warily perhaps" , "Watched with interest" .)