Snake artist follows horse (5)
I believe the answer is:
cobra
'snake' is the definition.
(I've seen this before)
'artist follows horse' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'follows' means one lot of letters go next to another.
'horse' becomes 'cob' (cob is a kind of horse).
'ra' after 'cob' is 'COBRA'.
(Other definitions for cobra that I've seen before include "Poisoner" , "Highly venomous hooded reptile" , "Deadly snake called King" , "Something with a hood" , "one leading charmed life?" .)