Work with leader of uprising, fast becoming rich (7)
I believe the answer is:
opulent
'rich' is the definition.
('opulent' can be similar in meaning to 'rich')
'work with leader of uprising fast' is the wordplay.
'work' becomes 'op' (abbreviation for opus**).
'with' says to put letters next to each other.
'leader of' indicates taking the first letters.
'fast' becomes 'lent' (I've seen this before).
The first letter of 'uprising' is 'u'.
'op'+'u'+'lent'='OPULENT'
'becoming' is the link.
(Other definitions for opulent that I've seen before include "Prosperous" , "No let-up (anag)" , "extremely elegant" , "Well-to-do or lavish" , "'Rich, sumptuous (7)'" .)