start a hare

• start a hare running

From the once common practice of hunting rabbits for sport.

start a hare (third-person singular simple present starts a hare, present participle starting a hare, simple past and past participle started a hare)

1. (UK, dated) To introduce a conversational topic.

• start a fresh hare

• “start a hare”, in Collins English Dictionary.
• “start a hare” in Idioms and phrases, TheFreeDictionary.com, Huntingdon Valley, Pa.: Farlex, Inc., 2003–2024.