Gemstone being worn by Yankee with Times (4)
I believe the answer is:
onyx
'gemstone' is the definition.
(I know that onyx is a type of calcedony)
'worn by yankee with times' is the wordplay.
'worn by' becomes 'on'.
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' is a charade indicator (letters next to each other).
'times' becomes 'x' (x resembles the multiplication or times sign).
'on'+'y'+'x'='ONYX'
'being' is the link.
(Other definitions for onyx that I've seen before include "Semi-precious variety of agate" , "Banded chalcedony" , "Black variety of quartz" , "Black and white striped gemstone" , "Stones" .)