Discovers money makes money (6)
I believe the answer is:
learns
'discovers' is the definition.
('learn' can be a synonym of 'discover')
'money makes money' is the wordplay.
'money' becomes 'l' (L can mean 'pounds').
'makes money' becomes 'earns' (I've seen this in another clue).
'l'+'earns'='LEARNS'
(Other definitions for learns that I've seen before include "Acquires knowledge or skills" , "Teaches non-standard" , "Finds out" , "Gains knowledge or skill" , "Imbibes knowledge" .)