Horse, an old joke (8)

I believe the answer is:

chestnut

I believe this is a double definition.

'horse' is the first definition.
(I know that chestnut is a type of horse)

'an old joke' is the second definition.
(as in an old chestnut)

(Other definitions for chestnut that I've seen before include "Golden to reddish brown colour" , "Wooden" , "comedian's overused line?" , "Item for stuffing" , "Dark golden-brown horse" .)

I've seen this clue in The Times.

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