Time construction worker set off (7)
I believe the answer is:
trigger
'set off' is the definition.
(synonyms)
'time construction worker' is the wordplay.
'time construction' becomes 't' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'worker' becomes 'rigger' (rigger is a kind of worker).
't'+'rigger'='TRIGGER'
Can you help me to learn more?
(Other definitions for trigger that I've seen before include "Part of gun" , "make things happen" , "Roy Rogers' horse" , "Activating device" , "Pull it to discharge gun" .)