A crock if i heard one - Tradução em português

Good night everybody,

I'm studying English yet and so I have been using this forum so much and is helping me a lot. Good job!

This is my first post here at this forum and I would like if you could translate this phrase for me.

I saw it on a book and I didn't understand what this mean.

I appreciate your help.

Thanks in advance

p.s: You can correct me if I made some mistakes.