Student or Learner
I looked up that Idiom in the website and I didn't find it, so I looked it up in the internet and found that according to have sb in stitches | idiomcenter.com the meaning of the expression is: to cause somebody laugh a lot.
I hope it's helpful for anybody who was looking for the idiom and didn't find it in any dictionary.
I look it in Cambridge Dictionary, Oxford, wordreference.com, etc... the thing is that I was looking for it as I found it on a book: to have somebody in stitches....
Thanks for replying!