Arrives on horseback with purse I'd mislaid (5,2)
I believe the answer is:
rides up
'arrives on horseback' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'with purse i'd mislaid' is the wordplay.
'with' is a charade indicator (letters next to each other).
'mislaid' indicates an anagram.
'purse' next to 'id' is 'purseid'.
'purseid' with letters rearranged gives 'RIDES UP'.
Can you help me to learn more?
(Other definitions for rides up that I've seen before include "Lifts with wear" , "garment slowly rises" .)