Spooner's horse food powdered for dog (9)
I believe the answer is:
greyhound
'dog' is the definition.
(greyhound is a kind of dog)
'spooner's horse food powdered' is the wordplay.
I cannot really see how this works, but
'horse' could be 'grey' (I've seen this before) and 'grey' is located in the answer.
'food' could be 'd' (D is an example) and 'd' is located in the answer.
This may be the basis of clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for greyhound that I've seen before include "Speedy dog" , "racer" , "Dog trained for racing on tracks" , "Want to bet on it?" , "Swift breed of dog" .)