Grin about jewellery (4)
I believe the answer is:
ring
'jewellery' is the definition.
(ring is a kind of jewellery)
'grin about' is the wordplay.
'about' indicates anagramming the letters.
'grin' is an anagram of 'RING'.
(Other definitions for ring that I've seen before include "0?" , "Form circle around" , "Hoop" , "Circus space; surround" , "place for fight" .)