Changing gear, time to leave (8)
I believe the answer is:
emigrate
'leave' is the definition.
(thesaurus)
'changing gear time' is the wordplay.
'changing' indicates an anagram.
'gear'+'time'='geartime'
'geartime' is an anagram of 'EMIGRATE'.
'to' is the link.
(Other definitions for emigrate that I've seen before include "Settle overseas" , "Go to settle in a foreign country" , "Permanently leave" , "Go to live and work in another country" , "Tiger Mae has gone abroad to live, oddly" .)