Tax responsibility (4)

I believe the answer is:

duty

This clue is a double definition.

'tax' is the first definition.
(duty can mean a tax or toll)

'responsibility' is the second definition.
(synonyms)

(Other definitions for duty that I've seen before include "charge" , "Moral/legal obligation" , "Moral or legal obligation" , "'Obligation, responsibility (4)'" , "Is one bound" .)

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

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