Hello, I was listening to a TED Talk and I found the verb to CLIP IN. The speaker was telling his experience when he fell off the bike. He said: "I didn't really remember how to ride a bike, I hadn't done it since I was a kid. So I crashed a lot. And I mean it's like you never forget, but that's like a total lie especially if you CLIP IN. It is like scary." What is the meaning of CLIP IN in this case? Thank you in advance for your answer.