Intrusion, once merchant moved out (12)

I believe the answer is:

encroachment

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'intrusion' is the definition.
(synonyms)

'once merchant moved out' is the wordplay.
'once merchant' can be anagrammed to 'ENCROACHMENT'.
However, I am not sure how this is indicated.

Can you help me to learn more?

(Other definitions for encroachment that I've seen before include "Gradual intrusion" , "An advance beyond expected limits" .)

I've seen this clue in The Daily Express.

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