Lop Naomi using a horse (8)
I believe the answer is:
palomino
'a horse' is the definition.
(palomino is a kind of horse)
'lop naomi using' is the wordplay.
'using' indicates anagramming the letters.
'lop'+'naomi'='lopnaomi'
'lopnaomi' is an anagram of 'PALOMINO'.
(Other definitions for palomino that I've seen before include "Golden horse with pale mane" , "White-maned horse of the southwest USA" , "Colour breed of horse" , "colt?" , "SW US horse breed" .)