In the morning, harassment of editors gradually paid off (9)
I believe the answer is:
amortised
'paid off' is the definition.
(amortising is a kind of paying off)
'in the morning harassment of editors gradually' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'morning' could be 'am' (as in 12:00 AM) and 'am' is located in the answer.
'of' could be 'o' and 'o' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for amortised that I've seen is " Written off over time".)