Gold piece in circulation? (5)
I believe the answer is:
orbit
'in circulation' is the definition.
(I've seen this before)
'gold piece' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'piece' becomes 'bit' (synonyms).
'or'+'bit'='ORBIT'
(Other definitions for orbit that I've seen before include "Field of influence" , "Path of planet around sun" , "Path of planet etc" , "Sun's circulation" , "Range of influence" .)