Clue: Sound made by horse shedding weight at the start, or another equine (5)
Answer: HINNY
Explanation: Definition: another equine
A subtraction: [w]HINNY ('sound made by horse') minus the initial W ('shedding **W**eight at the start'), for the cross of a stallion and a jenny, a female donkey (as opposed to a mule, which has a donkey for father, and mare for mother).