Live with desire to fit in (6)
I believe the answer is:
belong
'fit in' is the definition.
(I've seen this before)
'live with desire' is the wordplay.
'live' becomes 'be' (synonyms).
'with' is a charade indicator (letters next to each other).
'desire' becomes 'long' (longing is a kind of desiring).
'be'+'long'='BELONG'
'to' is the link.
(Other definitions for belong that I've seen before include "Be the property of" , "accepted socially" , "Be correctly assigned" , "Be rightly assigned (to)" , "Pertain" .)