Polynesian painter holding a horse's head (8)
I believe the answer is:
tahitian
'polynesian' is the definition.
(Tahitian is an example)
'painter holding a horse's head' is the wordplay.
'painter' becomes 'titian' (Titian is an example).
'holding' indicates putting letters inside.
'head' suggests taking the first letters.
The initial letter of 'horses' is 'h'.
'a'+'h'='ah'
'titian' enclosing 'ah' is 'TAHITIAN'.
(Other definitions for tahitian that I've seen before include "One from Papeete" , "Polynesian islander" , "inhabitant of island" , "It, in a hat (anag)" , "someone on tropic island" .)