Finished shot transmission device (9)

I believe the answer is:

overdrive

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'transmission device' is the definition.
'overdrive' can be an answer for 'device' (overdrive is a kind of device). I'm unsure of the 'transmission' bit.

'finished shot' is the wordplay.
'finished' becomes 'over' (over can mean finished or ended).
'shot' becomes 'drive' (drive is a kind of shot).
'over'+'drive'='OVERDRIVE'

Can you help me to learn more?

(Other definitions for overdrive that I've seen before include "It gets you going fast" , "Engine mechanism" , "State of excessive activity" , "Find extra gear" , "Furious activity" .)

I've seen this clue in the Sydney Morning Herald.

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