Fib to disloyal gangster (9)
I believe the answer is:
falsehood
'fib' is the definition.
(thesaurus)
'disloyal gangster' is the wordplay.
'disloyal' becomes 'false' ('false' is associated in meaning with 'disloyal').
'gangster' becomes 'hood' (I've seen this before).
'false'+'hood'='FALSEHOOD'
'to' acts as a link.
(Other definitions for falsehood that I've seen before include "Deception" , "It might be hard to swallow" , "Has fooled with lie" , "Pork pie" , "Untruth" .)