Refuse to carry hard kind of metal (6)
I believe the answer is:
thrash
'kind of metal' is the definition.
(thrash metal is a genre of music)
'refuse to carry hard' is the wordplay.
'refuse' becomes 'trash' (I've seen this before).
'to carry' is an insertion indicator.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'trash' going around 'h' is 'THRASH'.
(Other definitions for thrash that I've seen before include "Clobber" , "Beat heavily, perhaps with whip" , "Beat violently" , "tan" , "Beat up, batter" .)