Compensate by sending a note (5)
I believe the answer is:
atone
'compensate' is the definition.
(I know that atone is a more specific form of compensate)
'sending a note' is the wordplay.
'sending' indicates an anagram (letters are sent to different positions).
'a'+'note'='anote'
'anote' with letters rearranged gives 'ATONE'.
'by' acts as a link.
(Other definitions for atone that I've seen before include "Make amends, being at one" , "Turn away from sin and do penance" , "Make up, compensate (for)" , "Pay the price" , "Adopt a cause" .)