Number in film in New York (6)
I believe the answer is:
ninety
'number' is the definition.
(ninety is a kind of number)
'in film in new york' is the wordplay.
'film' becomes 'ET' (E.T. the Extra-Terrestrial).
'in' means one lot of letters goes inside another.
'new york' becomes 'ny'.
'in'+'et'='inet'
'inet' inserted into 'ny' is 'NINETY'.
(Other definitions for ninety that I've seen before include "Minutes played in a football match" , "XC (in ancient Rome)" , "Excellent percentage score" , "old age" , "Fourscore and ten" .)