Thrash metal legal? Forbidden covers sent west (10)
I believe the answer is:
flagellate
'thrash' is the definition.
(thesaurus)
'metal legal? forbidden covers sent west' is the wordplay.
'covers' indicates the answer is hidden within the clue (I've seen 'covered' mean this (the answer is covered up by the clue)).
'sent west' says the letters should be written backwards (letters written left to right or 'east to west').
'etallegalf' can be found hidden inside 'metal legal forbidden'.
'etallegalf' written backwards gives 'FLAGELLATE'.
(Other definitions for flagellate that I've seen before include "Whip" , "Scourge" .)