Plan to spend a penny? (3-2-3-2)

I believe the answer is:

pay-as-you-go

I believe this clue is a double definition.

'plan' is the first definition.
(no subscription - pay for what you use e.g. phone)

'to spend a penny?' is the second definition.
('go' can mean use the toilet - cryptic definition)

I've seen this clue in The Everyman puzzle in The Observer.

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