It's natural to see a robin round about the start of Noel (6)
I believe the answer is:
inborn
'it's natural to' is the definition.
(thesaurus)
'a robin round about the start of noel' is the wordplay.
'round' is an anagram indicator.
'about' indicates putting letters inside.
'the start of' suggests taking the first letters.
The initial letter of 'noel' is 'n'.
'robin' is an anagram of 'iborn'.
'iborn' enclosing 'n' is 'INBORN'.
'see' acts as a link.
(Other definitions for inborn that I've seen before include "naturally!" , "Existing from birth; innate" , "Innate, natural" , "Congenital" , "that's natural" .)