Dust disturbed by horse (4)
I believe the answer is:
stud
'horse' is the definition.
(I know that stud is a type of entire)
'dust disturbed' is the wordplay.
'disturbed' indicates an anagram (the order of letters is disturbed).
'dust' is an anagram of 'STUD'.
'by' is the link.
(Other definitions for stud that I've seen before include "Virile man" , "Collar button or horse farm" , "Horse-breeding farm" , "Macho - stables - boss" , "Macho - stable - boss" .)