Groom takes horse round Epsom finally (4)
I believe the answer is:
comb
'groom' is the definition.
(combing is a kind of grooming)
'horse round epsom finally' is the wordplay.
'horse' becomes 'cob' (cob is a kind of horse).
'round' indicates putting letters inside.
'finally' says to take the final letters.
The final letter of 'epsom' is 'm'.
'cob' going around 'm' is 'COMB'.
'takes' is the link.
(Other definitions for comb that I've seen before include "Fowl's crest" , "Device for tidying one's appearance" , "Toothed grooming implement" , "Toothed device - crest" , "Untangle (hair)" .)