Assembled, but out around half a mile! (5)

I believe the answer is:

built

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'assembled' is the definition.
(synonyms)

I don't understand how the rest of the clue works.

(Other definitions for built that I've seen before include "assembled" , "Erected" , "Constructed" , "Raised" , "Made by combining materials and parts" .)

I've seen this clue in the Evening Standard.

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