Lover of metal car was made to conserve energy at first (10)

'lover of metal' is the definition.
(fan of heavy metal music)

'car was made to conserve energy at first' is the wordplay.
'car' becomes 'banger' (I have seen 'Old car ' mean 'banger' so perhaps 'car' could also mean 'banger').
'was made' becomes 'had' (having to do a thing can mean being made to do it).
'to conserve' means one lot of letters goes inside another.
'energy' becomes 'e' (physics symbol as in E=mca).
'at first' means one lot of letters go next to another.
'had' placed around 'e' is 'head'.
'banger' after 'head' is 'HEADBANGER'.