Annoy headless currency of Russia (6)

I believe the answer is:

rouble

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

'currency of russia' is the definition.
'rouble' can be an answer for 'currency' (Russian rouble). I'm not certain of the 'of russia' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for rouble that I've seen before include "ready in Belarus" , "Russian bread" , "Monetary unit of Russia" , "Unit of money in Russia" , "bread from abroad" .)

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

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