After time, one fitting out ship set off (7)

I believe the answer is:

trigger

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'set off' is the definition.
('trigger' can be a synonym of 'set off')

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

Can you help me to learn more?

(Other definitions for trigger that I've seen before include "Cause (device) to operate" , "Roy Rogers' horse" , "trip" , "Gun release mechanism" , "Initiate" .)

I've seen this clue in The Telegraph.

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