Earn a note on the side (4)
I believe the answer is:
wing
'the side' is the definition.
(I've seen this in other clues)
'earn a note on' is the wordplay.
'earn' becomes 'win'.
'a note' becomes 'g' (musical note).
'on' means one lot of letters go next to another.
'win'+'g'='WING'
(Other definitions for wing that I've seen before include "Arm of building or bird" , "Appendage aiding flight" , "Feathered limb used in flying" , "bit of a mansion" , "Flying part" .)