Rapid series of visits organised to Welsh pits and to old city (7-4,4)

I believe the answer is:

whistle-stop tour

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

'rapid series of visits' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'organised to welsh pits and to old city' is the wordplay.
'organised' indicates anagramming the letters.
'and' says to put letters next to each other.
'old city' becomes 'ur' (ancient city state).
'to'+'welsh'+'pits'='towelshpits'
'towelshpits' is an anagram of 'whistlestop'.
'whistlestop'+'to'+'ur'='WHISTLE-STOP TOUR'

Can you help me to learn more?

I've seen this clue in The Times.

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.