Cut down what many were due to pay (5)
I believe the answer is:
mowed
'cut down' is the definition.
(I've seen this in another clue)
'what many were due to pay' is the wordplay.
I cannot really understand how this works, but
'many' could be 'm' (Roman numeral for a thousand) and 'm' is found within the answer.
'were' could be 'owed' (owing is a kind of being) and 'owed' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for mowed that I've seen is " Cut the grass".)