Carried out beginning of dredging at back of river passage close to Carlisle (8)

I believe the answer is:

executed

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

I don't understand the remainder of the clue.

(Other definitions for executed that I've seen before include "Performed" , "Lawfully killed" , "Beheaded" , "Put to death as punishment" , "Carried out the task or put to death" .)

I've seen this clue in The Independent.

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