Distorts notes added after hostilities (5)
I believe the answer is:
warps
'distorts notes' is the definition.
'warps' can be an answer for 'distorts' ('warp' can be a synonym of 'distort'). I'm unsure of the 'notes' bit.
'added after hostilities' is the wordplay.
'added' becomes 'ps' (I can't justify this - if you can you should give a lot more credence to this answer).
'after' is a charade indicator (letters next to each other).
'hostilities' becomes 'war' (hostilities between two nations).
'ps' put after 'war' is 'WARPS'.
Can you help me to learn more?
(Another definition for warps that I've seen is " Becomes distorted".)