Joke after time beset by extra financial burden (8)
I believe the answer is:
mortgage
'financial burden' is the definition.
(a mortgage is a loan)
'joke after time beset by extra' is the wordplay.
'joke' becomes 'gag' (a gag is a joke or witticism).
'after' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'beset by' is an insertion indicator ('beset' could historically mean 'cover').
'extra' becomes 'more' (both can mean additional).
'gag' after 't' is 'tgag'.
'tgag' inserted into 'more' is 'MORTGAGE'.
(Other definitions for mortgage that I've seen before include "Transfer of property rights as security for a loan" , "borrowing arrangement" , "Home loan" , "Loan secured against property" , "Borrowing agreement" .)