Unexpected departures artlessly scanned (7)

I believe the answer is:

perused

'scanned' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for perused that I've seen before include "Browsed" , "Studied" , "Read (something) very carefully" , "Scanned" .)

I've seen this clue in The Guardian.

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