Impressive old gold coin (5)
I believe the answer is:
noble
I believe this is a double definition.
'impressive' is the first definition.
(similar in meaning)
'old gold coin' is the second definition.
(I've seen this before)
(Other definitions for noble that I've seen before include "Former gold coin" , "Having high moral qualities" , "Person of high rank" , "Worthy" , "Illustrious - old money" .)