Bean that may well feature in a vegetarian’s diet (3)

I believe the answer is:

nut

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'bean' is the definition.
(thesaurus)

I can't explain the rest of the clue.

(Other definitions for nut that I've seen before include "Combines with bolt to secure" , "Hard-shelled fruit or informal eccentric" , "Head (sl.)" , "1A [CRACKPOT]?" , "Bolt counterpart" .)

I've seen this clue in the Evening Standard.

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