Friendly guy introduced by a note (8)
I believe the answer is:
amicable
'friendly' is the definition.
('amicable' is associated in meaning with 'friendly')
'guy introduced by a note' is the wordplay.
'guy' becomes 'cable' (I've seen this in other clues).
'introduced by' is a charade indicator (letters next to each other).
'a note' becomes 'ami' (I can't explain this - if you can you should believe this answer much more).
'cable' put after 'ami' is 'AMICABLE'.
Can you help me to learn more?
(Other definitions for amicable that I've seen before include "sweet?" , "cordial" , "Friendly, peaceful" , "Friendly, nonthreatening" , "not hostile" .)