Answer: The clown is commenting on the cyclic nature of time and saying that Malvolio has received the treatment he deserved.
Explanation: In the bolded line, "whirligig" means an object or part of an object that spins or whirls. "And thus the whirligig of time brings in his revenges" becomes a metaphor for the saying "what goes around, comes around" and "you reap what you sow".
