We're paying for liability (4)

I believe the answer is:

onus

'for liability' is the definition.
(I've seen this in another clue)

I don't understand the remainder of the clue.

(Other definitions for onus that I've seen before include "'Burden, load (4)'" , "Responsibilty" , "albatross?" , "Burden, duty" , "Weight of responsibility" .)

I've seen this clue in The Guardian.

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