Money made on one's large account principally (5)
I believe the answer is:
moola
'money' is the definition.
(informal term for money)
'made on one's large account principally' is the wordplay.
'principally' indicates taking the first letters.
The initial letters of 'made on ones large account' is 'MOOLA'.
(Other definitions for moola that I've seen before include "Dosh, dough" , "Money (slang)" , "Ackers, lolly" , "11 [lolly]" .)