Look round New York - it's crazy (5)
I believe the answer is:
loony
'crazy' is the definition.
(I know that crazy can be written as loony)
'look round new york' is the wordplay.
'look' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'round' becomes 'o' (round can mean a round object).
'new york' becomes 'ny'.
'lo'+'o'+'ny'='LOONY'
'it's' acts as a link.
(Other definitions for loony that I've seen before include "Nuts" , "Crazy" , "mad" , "Silly" .)