"To follow fashion" has a very wide application and could mean a number of things.
"Fashion" as a noun tends to refer to the current popular style of clothes, hair, or any other form of dress or grooming. However, it can also be applied to any trend made popular either by a majority, or among a specific group.
A "follower of fashion" is someone that goes along with a trend, or most trends.
I think a worthwhile pop-culture reference here is The Kinks song "Dedicated Follower of Fashion":
And when he does his little rounds
'Round the boutiques of London Town
Eagerly pursuing all the latest fads and trends
'Cause he's a dedicated follower of fashion
"Follower of fashion" is sometimes used in the pejorative sense because, like the modern term "sheeple", those who follow trends are seen by some not to have a mind of their own.
Context is everything though, so if you "fashion" to mean something other than dress and grooming (eg a behaviour), naturally the "follower" means something different too. It could mean "follow" in the sense of "keeping up with" academically, ie reading fashion news, but it seems very unlikely when there is the widely used and accepted definition that I have detailed. I would never have assumed that it meant that, unless context suggested otherwise.