Source of tremendous intelligence? No! (4)
I believe the answer is:
twit
'source of tremendous intelligence? no' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'source of tremendous intelligence?' is the wordplay.
'source of' suggests taking the first letters.
'intelligence?' becomes 'wit' (wit is a kind of intelligence).
The first letter of 'tremendous' is 't'.
't'+'wit'='TWIT'
(Other definitions for twit that I've seen before include "Ninny" , "Twerp" , "Idiot; tease" , "Tease - fool" , "Silly person; tease" .)