Stone bull seen around New York (4)
I believe the answer is:
onyx
'stone' is the definition.
(type of gemstone)
'bull seen around new york' is the wordplay.
'bull' becomes 'ox'.
'seen around' is an insertion indicator.
'new york' becomes 'ny'.
'ox' enclosing 'ny' is 'ONYX'.
(Other definitions for onyx that I've seen before include "Kind of agate" , "Stones" , "Stone-like marble with coloured layers" , "Banded gemstone" , "Semi-precious variety of agate" .)