a hobby horse

hobby-horse

A subject, topic, or issue about which one frequently or incessantly talks, expounds, or complains. Ah, here we go again. Once grandpa gets on his hobby-horse about the government, there's no stopping him!

a ˈhobby horse

a subject that somebody feels strongly about and likes to talk about: Sorry, I’m starting to get on my hobby horse! (= talk about my favourite subject).
See also: hobby, horse
References in periodicals archive ?
There are numerous videos on YouTube about how to make a hobby horse, and the components are easy to find: a broomstick, fabric, fur, wool, stuffing and decorations - which are obviously up to each creator.
A hobby horse pattern (Cut out the hobby horse shown here.
I want (my children) to have an appreciation of the differences between yesterday and today,'' said Reed as her toddler daughter clung to a hobby horse.