Survive south during leave (5)
I believe the answer is:
exist
'survive' is the definition.
(synonyms)
'south during leave' is the wordplay.
'south' becomes 'S' (synonyms).
'during' means one lot of letters goes inside another.
'leave' becomes 'exit' (synonyms).
's' going inside 'exit' is 'EXIST'.
(Other definitions for exist that I've seen before include "Survive" , "quick!" , "Get a life!" , "Live" , "Have being or continue living" .)