Lewis being one is extremely likeable (4)
I believe the answer is:
isle
'lewis' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?
'one is extremely likeable' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'likeable' with its middle removed is 'le'.
'is'+'le'='ISLE'
'being' acts as a link.
Can you help me to learn more?
(Other definitions for isle that I've seen before include "9 ac perhaps" , "Geographic location" , "Man, for one" , "___ of Dogs, Man or Skye" , "Wight, Man or Skye" .)