Note slipped inside gift for master (8)
I believe the answer is:
dominate
'for master' is the definition.
(synonyms)
'note slipped inside' is the wordplay.
'note' becomes 'mi' (as in do-re-mi).
'slipped' becomes 'donate' (I can't explain this - if you can you should believe this answer much more).
'inside' means one lot of letters goes inside another.
'mi' going into 'donate' is 'DOMINATE'.
'gift' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for dominate that I've seen before include "Admit one in order to be in control" , "Tower over" , "Rule" , "Master" , "corner" .)