Persons of interest may be at this jumbo (5)

I believe the answer is:

large

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

I cannot understand how the rest of the clue works.

(Other definitions for large that I've seen before include "Sizeable" , "Huge" , "Wide-ranging" , "Bulky" , "Strapping" .)

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

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