Her guy, Don, disturbed dog (9)
I believe the answer is:
greyhound
'dog' is the definition.
(greyhound is a kind of dog)
'her guy don disturbed' is the wordplay.
'disturbed' indicates anagramming the letters (the order of letters is disturbed).
'her'+'guy'+'don'='herguydon'
'herguydon' anagrammed gives 'GREYHOUND'.
(Other definitions for greyhound that I've seen before include "slender runner?" , "Want to bet on it?" , "Dog trained for racing on tracks" , "racer" , "Speedy dog" .)