Smart way to get fit in New York (5)
I believe the answer is:
nifty
'smart' is the definition.
(nifty can mean stylish)
'way to get fit in new york' is the wordplay.
'way to get' indicates an anagram (a way to have the letters).
'in' is an insertion indicator.
'new york' becomes 'ny'.
'fit' anagrammed gives 'ift'.
'ift' placed within 'ny' is 'NIFTY'.
(Other definitions for nifty that I've seen before include "Smart" , "Fine (slang)" , "Clever; stylish" , "Slick" , "Fast and neat" .)