Good coin and euro reduced in splendour (8)
I believe the answer is:
grandeur
'splendour' is the definition.
(synonyms)
'good coin and euro reduced' is the wordplay.
'good' becomes 'g' (abbreviation).
'coin' becomes 'rand' ().
'and' means one lot of letters go next to another.
'reduced' means to remove the last letter.
'euro' with its last letter taken away is 'eur'.
'g'+'rand'+'eur'='GRANDEUR'
'in' is the link.
(Other definitions for grandeur that I've seen before include "The splendour of France" , "Augustness" , "state" , "Loftiness" , "Magnificence - rare dung (anag)" .)