Wendy was a prostitute.

Wendy was a prostitute and didn't want her granny to know.
One day police came across the brothel that she worked at and ordered all prostitutes to stand in a line, so that they could take their names one by one.
Suddenly, granny comes along and notices Wendy in the line which was now leading outside, and so she walked up to her and said.
"Wendy dear, why are you standing in this line full of prostitutes?"
Wendy lied and told granny that the police were giving out free oranges, and she wanted some.
"That's nice." Said granny and so she went to to back of the line as she wanted some for herself.
Eventually the police get to her and say "Tut tut tut, still at it your age old lady, how do you do it?"
Granny smiles and simply replies "It's easy dear, I just pull the skin back and suck them dry!"