Crossword Genius

Steals money from castles (5)

Ross

I believe the answer is:

rooks

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

'castles' is the definition.
(I know this)

'steals money from' is the wordplay.
I cannot quite understand how this works, but
'from' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
The remaining letters 'roks' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

(Other definitions for rooks that I've seen before include "Collective name for them is a parliament" , "Castles, also, in chess" , "Cheats" , "Overcharges" , "men on the board" .)

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