He's funny, as many will admit (5)
I believe the answer is:
clown
'he's funny' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'many will admit' is the wordplay.
'many will' becomes 'cl' (I can't justify this - if you can you should give a lot more credence to this answer).
'admit' becomes 'own' (own can mean to admit or acknowledge).
'cl'+'own'='CLOWN'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for clown that I've seen before include "Red-nosed, long-shoed entertainer" , "Buffoon" , "Funny man in circus" , "Behave playfully" , "Harlequin" .)