Not much evidence that there's a horse around (4,1,3)

'horse around' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'not much evidence that there's a' is the wordplay.
I cannot really see how this works, but
'a' is within the answer.
'not much' could be 'bit' and 'bit' is found in the answer.
The remaining letters 'just' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?