Pay for sending a note (5)
I believe the answer is:
atone
'pay for' is the definition.
(I've seen this before)
'sending a note' is the wordplay.
'sending' is an anagram indicator (letters are sent to different positions).
'a'+'note'='anote'
'anote' anagrammed gives 'ATONE'.
(Other definitions for atone that I've seen before include "Make reparation for a misdeed" , "In agreement - sounds singular" , "Make up for wrong done" , "Recompense" , "Turn away from sin and do penance" .)