Man being one is extremely likeable (4)
I believe the answer is:
isle
'man' is the definition.
(I've seen this before)
'one is extremely likeable' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'likeable' with its centre taken out is 'le'.
'is'+'le'='ISLE'
'being' is the link.
(Other definitions for isle that I've seen before include "''There is an ..., a bonny ...'' (anthem of Shannon RFC)" , "Small seabound place" , "Man, possibly" , "Sea-girt area" , "isolated spot" .)