Former gold coin of imposing appearance (5)
I believe the answer is:
noble
This might be a double definition.
'former gold coin' is the first definition.
(I've seen this before)
'imposing appearance' is the second definition.
'noble' can be an answer for 'imposing' (I've seen this before). I am unsure of the 'appearance' bit.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for noble that I've seen before include "Having high moral qualities" , "eg Earl" , "titled person" , "fine" , "Honourable or of high rank" .)