Adjust rate while becoming richer (9)
I believe the answer is:
wealthier
'richer' is the definition.
('wealthy' can be similar in meaning to 'rich')
'adjust rate while' is the wordplay.
'adjust' indicates anagramming the letters.
'rate'+'while'='ratewhile'
'ratewhile' anagrammed gives 'WEALTHIER'.
'becoming' is the link.
(Other definitions for wealthier that I've seen before include "More loaded" , "More well-off" .)