Covered the joint, maybe? (5)

I believe the answer is:

cased

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'covered' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

(Other definitions for cased that I've seen before include "Carefully inspected (for crime)" , "Reconnoitred (sl.)" , "Covered, protected; checked over (by robber)" , "put in a box" , "examined with intention to rob" .)

I've seen this clue in the Evening Standard.

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