Number I catch in New York (6)
I believe the answer is:
ninety
'number' is the definition.
(ninety is a kind of whole number)
'i catch in new york' is the wordplay.
'catch' becomes 'net' (net can mean to catch).
'in' means one lot of letters goes inside another.
'new york' becomes 'ny'.
'i'+'net'='inet'
'inet' inserted within 'ny' is 'NINETY'.
(Other definitions for ninety that I've seen before include "Four score and ten" , "quite an age" , "Quantity" , "XC (in ancient Rome)" , "Minutes played in a football match" .)