Bishop is enclosing doubly large invoices (5)
I believe the answer is:
bills
'invoices' is the definition.
('bill' can be a synonym of 'invoice')
'bishop is enclosing doubly large' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'enclosing' means one lot of letters goes inside another.
'doubly' says to double the letters.
'large' becomes 'L' (eg in clothes sizes).
'l' duplicated is 'll'.
'is' enclosing 'll' is 'ills'.
'b'+'ills'='BILLS'
(Other definitions for bills that I've seen before include "Beaks" , "Draft laws" , "Invoices" .)