Compensate for firm having cancelled earlier (6)
I believe the answer is:
offset
'compensate for' is the definition.
(I've seen this before)
'firm having cancelled earlier' is the wordplay.
I cannot quite understand how this works, but
'firm' could be 'set' (both can mean fixed) and 'set' is found in the answer.
'cancelled' could be 'off' (similar in meaning) and 'off' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for offset that I've seen before include "Type of printing of efts" , "make an effort" , "Place out of line" , "Amount by which a thing is out of line" , "Compensation - printing process" .)