Agile one on foot in New York (5)
I believe the answer is:
nifty
'agile' is the definition.
(I've seen this before)
'one on foot in new york' is the wordplay.
'one' becomes 'I' (Roman numeral).
'on' means one lot of letters go next to another.
'foot' becomes 'ft' (synonyms).
'in' is an insertion indicator.
'new york' becomes 'ny'.
'i'+'ft'='ift'
'ift' put within 'ny' is 'NIFTY'.
(Other definitions for nifty that I've seen before include "Stylish, nimble" , "Smart" , "Really good (slang)" , "Quick - stylish" , "Fast and neat" .)