There's no commoner old coin (5)
I believe the answer is:
noble
'old coin' is the definition.
(I've seen this before)
'there's no commoner' is the wordplay.
'there's' is a charade indicator (letters next to each other).
'commoner' becomes 'ble' (I can't explain this - if you can you should believe this answer much more).
'no' next to 'ble' is 'NOBLE'.
Can you help me to learn more?
(Other definitions for noble that I've seen before include "Having high moral character" , "Possibly count" , "fine" , "Imposing, magnificent" , "Stately" .)