Villain is protected by a supporter repeatedly? Nonsense! (11)
I believe the answer is:
abracadabra
'nonsense' is the definition.
(abracadabra is a kind of nonsense)
'villain is protected by a supporter repeatedly?' is the wordplay.
'villain' becomes 'cad' (cad can mean a nasty person).
'is protected by' means one lot of letters goes inside another (inserted letters are held or protected).
'supporter' becomes 'bra' (a bra gives support to breasts).
'repeatedly?' shows that letters should be duplicated (I've seen 'repeatedly' mean this).
'a'+'bra'='abra'
'abra' doubled is 'abraabra'.
'cad' put inside 'abraabra' is 'ABRACADABRA'.
(Other definitions for abracadabra that I've seen before include "we hear as rabbit pulled from hat?" , "Magic word - gibberish!" , "for a spell it is declared" , "Charm" , "Magic word used by conjurors" .)