Fancy fool meeting with you and your setter (6)
I believe the answer is:
assume
'fancy' is the definition.
(thesaurus)
'fool meeting with you and your setter' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'meeting with' means one lot of letters go next to another.
'you' becomes 'u' (homophones).
'and' says to put letters next to each other.
'your setter' becomes 'me' (the person who set the crossword).
'ass'+'u'+'me'='ASSUME'
(Other definitions for assume that I've seen before include "Take for granted or take upon oneself" , "Take as read" , "Adopt or take for granted" , "Take to be the case" , "Take for granted or agreed" .)