Man, possibly to waste time, taking son for the day (4)
I believe the answer is:
isle
'man' is the definition.
(I've seen this before)
'taking son for the day' is the wordplay.
'taking' means one lot of letters goes inside another.
'son' becomes 's'.
'for the day' becomes 'ile' (I can't justify this - if you can you should give a lot more credence to this answer).
's' inserted into 'ile' is 'ISLE'.
'possibly to waste time' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for isle that I've seen before include "Detached place" , "Eg, Sheppey" , "somewhere surrounded by water" , "Sea-girt area" , "Man, maybe" .)