Unprepared to survive, so small (4,6)
I believe the answer is:
last minute
'unprepared' is the definition.
(last-minute can mean unprepared or improvised)
'survive so small' is the wordplay.
'survive' becomes 'last' (synonyms).
'so small' becomes 'minute' (minute can mean very small).
'last'+'minute'='LAST-MINUTE'
'to' is the link.
(Other definitions for last minute that I've seen before include "with no time to spare" , "rushed" , "right up to the deadline" , "done at 23:59?" , "Not properly prepared" .)