It'll help with smooth movement in musical piece (6,3)

I believe the answer is:

grease gun

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'it'll help with smooth movement' is the definition.
I can't judge whether this defines the answer.

'musical piece' is the wordplay.
'musical' becomes 'grease' (Grease is a film musical).
'piece' becomes 'gun' (slang term for a gun).
'grease'+'gun'='GREASE-GUN'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for grease gun that I've seen before include "Lubricant applicator" , "Lubricant applier" , "Lubricating device" , "Lubricating pump" .)

I've seen this clue in The Telegraph.

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