Crossword Genius

Our faction in revolt about king — who did this? (5)

Ross

I believe the answer is:

usurp

I'm a little stuck... Click here to teach me more about this clue!

'our faction' is the definition.
I can't tell whether this definition defines the answer.

'in revolt about king who did this?' is the wordplay.
I cannot quite see how this works, but
'king' could be 'r' (abbreviation for rex, king in Latin) and 'r' is found within the answer.
'in revolt' could be 'up' (I've seen this in other clues) and 'up' is found in the remaining letters.
The remaining letters 'us' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for usurp that I've seen before include "Seize without right" , "Take (power etc) illegally" , "Take power unlawfully" , "Oust" , "Seize wrongfully" .)

I've seen this clue in The Times.
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