English sheep turning into horse? (4)
I believe the answer is:
mare
'horse?' is the definition.
(mare is a kind of horse)
'english sheep turning' is the wordplay.
'english' becomes 'e' (abbreviation).
'sheep' becomes 'ram' (male sheep).
'turning' is a reversal indicator.
'e'+'ram'='eram'
'eram' backwards is 'MARE'.
'into' is the link.
(Other definitions for mare that I've seen before include "Female equine animal" , "Female quadruped" , "A night-time strangler" , "Horse; lunar sea" , "Nag" .)