Cost of enclosures carried by former partner, English (7)
I believe the answer is:
expense
'cost' is the definition.
(the cost or price of something)
'enclosures carried by former partner english' is the wordplay.
'enclosures' becomes 'pens' (pen is a kind of enclosure).
'carried by' means one lot of letters goes inside another.
'former partner' becomes 'ex' (an ex-partner).
'english' becomes 'E' (abbreviation).
'ex'+'e'='exe'
'pens' going into 'exe' is 'EXPENSE'.
'of' is the link.
(Other definitions for expense that I've seen before include "Incurred cost" , "Disbursal" , "damage" , "Outlay or cost" , "Disbursement" .)