Crossword Genius

What an agitator may do in prison? (4)

Ross

I believe the answer is:

stir

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

'prison?' is the definition.
(informal term for prison)

'what an agitator may do' is the wordplay.
I cannot quite understand how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is found in the answer.
The remaining letters 'str' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'in' acts as a link.

Can you help me to learn more?

(Other definitions for stir that I've seen before include "Whisk, blend" , "Wake; disturbance" , "Whisk or rouse" , "Awaken" , "Sensation" .)

I've seen this clue in the Evening Standard.
Want a hint initially instead of a full solution? Install my app