Noble is good currency (5)
I believe the answer is:
grand
'noble' is the definition.
('grand' can be similar in meaning to 'noble')
'good currency' is the wordplay.
'good' becomes 'g' (abbreviation).
'currency' becomes 'rand' (I've seen this before).
'g'+'rand'='GRAND'
'is' is the link.
(Other definitions for grand that I've seen before include "Designed to impress" , "Comprehensive" , "Stately - splendid" , "1000, colloquially" , "Majestic" .)