He's responsible for a better understanding of horses! (9)

'a better understanding of horses' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'he's' is the wordplay.
I cannot really see how this works, but
'he' could be 'smith' and 'smith' is present in the answer.
The remaining letters 'shoe' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'responsible for' is the link.

Can you help me to learn more?