Man (possibly): “I knocked off, finishing early” (4)
I believe the answer is:
isle
'man possibly' is the definition.
(Isle of Man is an example)
'i knocked off finishing early' is the wordplay.
'knocked off' becomes 'slew' (I've seen this in another clue).
'finishing early' means to remove the last letter (the word finishes earlier than normal).
'slew' with its final letter taken away is 'sle'.
'i'+'sle'='ISLE'
(Other definitions for isle that I've seen before include "Atoll" , "Detached place" , "Fair one is in shipping bulletin" , "somewhere surrounded by water" , "Isolated land" .)