A second quantity of money editor accepted (7)
I believe the answer is:
assumed
'accepted' is the definition.
('assume' can be a synonym of 'accept')
'a second quantity of money editor' is the wordplay.
'second' becomes 's' (common abbreviation).
'quantity of money' becomes 'sum' (as in a cash sum).
'editor' becomes 'ed' (abbreviation).
'a'+'s'+'sum'+'ed'='ASSUMED'
(Other definitions for assumed that I've seen before include "Taken as true; adopted" , "Took to be the case" , "thought" , "Took (control)" , "Bogus" .)