Hi Lilly, Hi Baloo
My thanks to you both for your answers, especially baloo! That's a better answer than could be found in a book

I think I understand what it means now and it seems to be a very useful construction to have in one's vocabulary. Thanks again to both of you for taking the time to answer me.
Lilly, I don't know if you want me to, but I can offer you two small corrections to your answer, which will make it sound much better English?
1)When you want to
say something, is better than when you want to
tell something.
Tell would be used if you had said ' When you want to
tell somebody something.
2) Also, you should have said
it means rather than
it's mean, which is not correct in this context. You could have said
it's meaning is, which is correct.
It's mean on the streets of New York , meaning it's tough on the streets of New York , is correct.
I hope this helps you as much as your answer helped me
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