Thrash metal not initially rocking that woman (7)
I believe the answer is:
leather
'thrash' is the definition.
(I've seen this before)
'metal not initially rocking that woman' is the wordplay.
'not initially' means to remove the first letter.
'rocking' indicates anagramming the letters.
'that woman' becomes 'her' (her refers to a woman).
'metal' with its first letter taken away is 'etal'.
'etal' with letters rearranged gives 'leat'.
'leat'+'her'='LEATHER'
(Other definitions for leather that I've seen before include "Morocco, perhaps" , "Polishing cloth" , "Flog; hide" , "Material made from animal skin" , "calf" .)