Of sound coins, maybe (5)
I believe the answer is:
sonic
'of sound' is the definition.
(I've seen this before)
'coins maybe' is the wordplay.
'maybe' is an anagram indicator.
'coins' with letters rearranged gives 'SONIC'.
(Other definitions for sonic that I've seen before include "Like mine, possibly" , "seven hundred and forty three mph!" , "Using waves" , "Travelling at Mach One" , "Sort of boom" .)