Serpent and Swan' by artist (5)
I believe the answer is:
cobra
'serpent' is the definition.
(I know that cobra is a type of elapid)
'swan by artist' is the wordplay.
'swan' becomes 'cob' (cob is a kind of swan).
'by' is a charade indicator (letters next to each other).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'cob'+'ra'='COBRA'
'and' is the link.
(Other definitions for cobra that I've seen before include "hamadryad" , "Venomous hooded snake" , "One with hood" , "Sinuous creature" , "Reptile (found in Cabinet Office Briefing Room A?)" .)