Demands fool accepts kilo (4)
I believe the answer is:
asks
'demands' is the definition.
('ask' can be a synonym of 'demand')
'fool accepts kilo' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'accepts' is an insertion indicator.
'kilo' becomes 'k' (phonetic alphabet: alpha, bravo, charlie etc.).
'ass' going around 'k' is 'ASKS'.
(Other definitions for asks that I've seen before include "Demands (something of someone)" , "Begs" , "Puts a question" , "Inquiries" , "Enquires; requests" .)