Conserving energy, got old motor a metal fan (10)

I believe the answer is:

headbanger

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'motor a metal fan' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'conserving energy got old' is the wordplay.
'conserving' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mca).
'got' becomes 'had' ('have' can be a synonym of 'get').
'old' becomes 'banger' (I can't explain this - if you can you should give a lot more credence to this answer).
'e' going within 'had' is 'head'.
'head'+'banger'='HEADBANGER'

Can you help me to learn more?

(Other definitions for headbanger that I've seen before include "crazy individual" , "Old music lover" , "Heavy-metal rock fan" .)

I've seen this clue in The Telegraph.

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