Back the favourites to make the pace (4)
I believe the answer is:
step
'the pace' is the definition.
(synonyms)
'back the favourites' is the wordplay.
'back' says the letters should be written backwards.
'the favourites' becomes 'pets' ('pet' can be a synonym of 'favourite').
'pets' back-to-front is 'STEP'.
'to make' is the link.
(Other definitions for step that I've seen before include "Stage - pace" , "Pace; foothold" , "one stage of flight" , "Prefix meaning related by remarriage" , "little walk?" .)