Criminal in store looting (7)

I believe the answer is:

pillage

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'looting' is the definition.
(thesaurus)

'criminal in store' is the wordplay.
'criminal' becomes 'lag' (slang term for a prisoner).
'in' means one lot of letters goes inside another.
'store' becomes 'pile' (I can't justify this - if you can you should believe this answer much more).
'lag' going into 'pile' is 'PILLAGE'.

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(Other definitions for pillage that I've seen before include "Violent stealing" , "Plunder, sack" , "Loot" , "Rob with violence" , "Sacking" .)

I've seen this clue in The Sun.

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