What's in Fashion was a small store, probably on Coxwell Ave. in East York.
What's in Fashion is one of a number of small stores that appear in the background of the opening scenes of the episode "Strings". These scenes were filmed on location on Coxwell Avenue in East York (now part of the amalgamated City of Toronto).
As Christie Black's mother gets off the bus, there is a car lying in wait for her outside What's in Fashion and The Friendly Butcher. The car accelerates past Wayne's Supermarket and Peter's Paint & Paper before knocking her down. She is then shot to make sure she was dead.
What's in Fashion seems to have gone out of business sometime since the filming of the episode.