Vacate it, using trigger (8)
I believe the answer is:
activate
'trigger' is the definition.
(synonyms)
'vacate it using' is the wordplay.
'using' indicates anagramming the letters (the letters used in a different way).
'vacate'+'it'='vacateit'
'vacateit' is an anagram of 'ACTIVATE'.
(Other definitions for activate that I've seen before include "Give life to" , "Switch on" , "Set off, trip" , "Put in motion" , "Cause to move or start" .)