Support of a flying prison (6)

I believe the answer is:

upkeep

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'support' is the definition.
(I know that upkeep is a type of support)

I don't understand the rest of the clue.

(Other definitions for upkeep that I've seen before include "payments?" , "Peek up at the maintenance" , "Maintenance costs" , "Cost of maintenance, say household" , "Running costs" .)

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

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