Heard superfans of activity with knights and horses (9)

I believe the answer is:

chestnuts

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'horses' is the definition.
(I know this)

I cannot understand how the remainder of the clue works.

(Other definitions for chestnuts that I've seen before include "often retold stories" , "horses" , "Common tree-fruits, sometimes roasted" , "Tree fruits called conkers - some are edible" .)

I've seen this clue in The Telegraph.

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