Refuse to accept source of intelligence and intellect (5)
I believe the answer is:
brain
'intellect' is the definition.
(brain is a kind of intellect)
'refuse to accept source of intelligence' is the wordplay.
'refuse' becomes 'bran' (I've seen this before**).
'to accept' indicates putting letters inside.
'source of' says to take the initial letters.
The initial letter of 'intelligence' is 'i'.
'bran' going around 'i' is 'BRAIN'.
'and' acts as a link.
(Other definitions for brain that I've seen before include "Thinking thing" , "Thinking organ" , "The grey matter" , "Intellectual ability" , "Haemorrhaging of talent" .)