Set off the first ship worker (7)
I believe the answer is:
trigger
'set off' is the definition.
(synonyms)
'first ship worker' is the wordplay.
'first ship' becomes 't' (I can't justify this - if you can you should believe this answer much more).
'worker' becomes 'rigger' (rigger is a kind of worker).
't'+'rigger'='TRIGGER'
'the' is the link.
Can you help me to learn more?
(Other definitions for trigger that I've seen before include "make things happen" , "Initiate" , "Gun-firing device" , "Releasing device" , "Part of gun" .)