Outcast quietly breaking wind from rear end (5)
I believe the answer is:
leper
'outcast' is the definition.
(I know that leper is a type of outcast)
'quietly breaking wind from rear end' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'breaking' means one lot of letters goes inside another.
'wind from rear end' becomes 'leer' (I am not sure about this - if you are sure you should believe this answer much more).
'p' put inside 'leer' is 'LEPER'.
Can you help me to learn more?
(Other definitions for leper that I've seen before include "sick person" , "Outcast, pariah" , "skin disease" , "Sufferer from dread disease, once made to wear bell" , "Social outcast" .)