About time to leave Arctic, possibly (5)
I believe the answer is:
circa
'about' is the definition.
(thesaurus)
'time to leave arctic possibly' is the wordplay.
'time' becomes 't'.
'to leave' is a deletion indicator.
'possibly' indicates anagramming the letters.
'arctic' with 't' removed is 'arcic'.
'arcic' with letters rearranged gives 'CIRCA'.
(Other definitions for circa that I've seen before include "Around (Latin)" , "Approximately (Latin)" , "Close to" , "Approximately (of a year)" , "Approximately, around" .)