Would driving force emu's tip to mutate? (7)

I believe the answer is:

impetus

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'would driving force' is the definition.
I can't tell whether this definition defines the answer.

'emu's tip to mutate?' is the wordplay.
'to mutate?' indicates an anagram (I've seen 'mutates' mean this).
'emus'+'tip'='emustip'
'emustip' is an anagram of 'IMPETUS'.

Can you help me to learn more?

(Other definitions for impetus that I've seen before include "Incentive - time's up (anag)" , "Catalyst" , "Imputes to force with which a body moves" , "Momentum, stimulus" , "Thrust" .)

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

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