A nut for the horse (3)

I believe the answer is:

cob

I believe this is a double definition.

'a nut' is the first definition.
(cob is a kind of nut)

'the horse' is the second definition.
(cob is a kind of horse)

'for' acts as a link.

(Other definitions for cob that I've seen before include "mount" , "Hazelnut" , "Swan of Jacobean origin" , "A loaf; a nut; a horse" , "Round loaf of bread" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app