By endless work advanced to become rich (7)
I believe the answer is:
opulent
'rich' is the definition.
(similar in meaning)
'by endless work advanced' is the wordplay.
'by' is a charade indicator (letters next to each other).
'endless' becomes 'u' (I am not sure about this - if you are sure you should believe this answer much more).
'work' becomes 'op' (common abbreviation for 'opus').
'advanced' becomes 'lent' (advance can mean to lend).
'u' put after 'op' is 'opu'.
'opu'+'lent'='OPULENT'
'to become' acts as a link.
Can you help me to learn more?
(Other definitions for opulent that I've seen before include "Let up on, being wealthy" , "Well-to-do or lavish" , "Wealthy, rich" , "'Loaded'" , "Ritzy" .)