Pace favourite's comeback (4)
I believe the answer is:
step
'pace' is the definition.
(I know that pace can be written as step)
'favourite's comeback' is the wordplay.
'favourite's' becomes 'pet's' ('pet' can be a synonym of 'favourite').
'comeback' says the letters should be written backwards.
'pets' written backwards gives 'STEP'.
(Other definitions for step that I've seen before include "Rung, dance movement" , "one stage of flight" , "Place foot on as with a pest" , "A pace for pets" , "bit of a dance" .)