Rich eccentric let up on (7)
I believe the answer is:
opulent
'rich' is the definition.
(similar in meaning)
'eccentric let up on' is the wordplay.
'eccentric' indicates an anagram.
'let'+'up'+'on'='letupon'
'letupon' is an anagram of 'OPULENT'.
(Other definitions for opulent that I've seen before include "Ritzy" , "magnificent" , "Well-to-do or lavish" , "Rolling" , "Wealthy, possessing riches" .)