I hit boxer. Silly show-off! (9)
I believe the answer is:
exhibitor
'show-off' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'i hit boxer silly' is the wordplay.
'silly' indicates anagramming the letters.
'i'+'hit'+'boxer'='ihitboxer'
'ihitboxer' is an anagram of 'EXHIBITOR'.
Can you help me to learn more?
(Other definitions for exhibitor that I've seen before include "showman" , "One showing items in gallery display" , "I hit boxer (anag.)" , "shower" , "One displaying (at show)" .)