Trouble shooter's money? (7)

I believe the answer is:

roubles

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'money?' is the definition.
(Russian money)

'trouble shooter's' is the wordplay.
'ROUBLES' is hidden in amongst the letters.
But, I am not sure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for roubles that I've seen before include "Currency" , "Moscow cash" , "Russian money" , "Russian monetary units" .)

I've seen this clue in the Evening Standard.

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