Takes horse say, and climbs rapidly (6,2)

'climbs rapidly' is the definition.
The definition and answer can be both related to change as well as being verbs in their -s form.
Maybe there's a link between them I don't understand?

'takes horse say' is the wordplay.
I cannot really understand how this works, but
'takes' could be 'shoots' ('shoot' can be a synonym of 'take') and 'shoots' is present in the answer.
The remaining letters 'up' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'and' acts as a link.

Can you help me to learn more?