Part of pay, especially? Yes (3)
I believe the answer is:
aye
'yes' is the definition.
(I've seen this before)
'part of pay especially?' is the wordplay.
'part of' says the answer is hidden in the clue.
'AYE' can be found hidden inside 'pay especially'.
(Other definitions for aye that I've seen before include "Yes, at the double for the sailor" , "Affirmative answer" , "Yes; ever" , "Always" , "An affirmative vote" .)