Give fellow a note (6)
I believe the answer is:
donate
'give' is the definition.
(donating is a kind of giving)
'fellow a note' is the wordplay.
'fellow' becomes 'don' (I've seen this before**).
'note' becomes 'te'.
'don'+'a'+'te'='DONATE'
(Other definitions for donate that I've seen before include "Give - present" , "Make a contribution" , "Make an offer" , "Muhammad -, US boxer" , "Give to a charity or good cause" .)