A pushful revolutionary (9)

I believe the answer is:

propeller

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'a pushful revolutionary' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

This is the entire clue.

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(Other definitions for propeller that I've seen before include "Driver" , "attachment on aircraft" , "Airscrew" , "Mechanical device" , "Screw (on a boat)" .)

I've seen this clue in The Globe and Mail.

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