Large expressions of doubts about terms of previous one-off payment (4,3)
I believe the answer is:
lump sum
'one-off payment' is the definition.
(a lump sump is a single payment)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for lump sum that I've seen before include "cash payout" , "Substantial payment" , "as pension may be part-paid?" , "Large payment, often in cash" , "chunk of bread?" .)