Favourite's backed for pace (4)
I believe the answer is:
step
'pace' is the definition.
('step' can be a synonym of 'pace')
'favourite's backed' is the wordplay.
'favourite's' becomes 'pets' ('pet' can be a synonym of 'favourite').
'backed' says the letters should be written in reverse.
'pets' reversed gives 'STEP'.
'for' is the link.
(Other definitions for step that I've seen before include "Section of flight" , "Tramp" , "Place foot on as with a pest" , "'Stage, rung (4)'" , "Pace - part of a procedure" .)