In "The Star Fraction" by Ken MacLeod, a Scottish science fiction author, a couple walks through a street and past a "trodie". The novel is set in Britain, so it may be a British expression. The street is in a future London.
"Jordan took her elbow and ostentatiously steered her past the trodie collapsed in the doorway of a Help the Waged charity shop."
Googling the expression didn't help. I can't find any reference to it in Cambridge.
It is the only occurence in the book (Kindle Edition) and after the scene there is no further reference to the word. It's not crucial to the plot, I'm just curious what it means.