Crossword Genius

What the knight does when his coach comes in? (5,2,5)

Ross

I believe the answer is:

jumps on board

I'm a little stuck... Click here to teach me more about this clue!

'what the knight' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'when his coach comes in?' is the wordplay.
I cannot quite see how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is located in the answer.
This explanation may well be incorrect...

'does' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.