Whenever a city has occasion (7)
I believe the answer is:
anytime
'whenever' is the definition.
(thesaurus)
'a city has occasion' is the wordplay.
'city' becomes 'NY' (short for New York).
'has' is a charade indicator (letters next to each other).
'occasion' becomes 'time' (I've seen this in another clue).
'a'+'ny'+'time'='ANYTIME'
(Other definitions for anytime that I've seen before include "At no particular moment" , "At whatever moment" , "date not fixed" , "A tiny me (anag.)" , "Whenever you like" .)