Forget about piggybacking on SFML's GLEW, it is going to get removed in 2.3 anyway.
Don't use GLEW either. Although many tutorials/guides/videos use GLEW, it has been proven to be slow, archaic in ways, and just loaded with too much stuff nobody should care about any more. What I would recommend is using one of the more "modern" ways of loading extensions: loader generators. You can find a few on the
OpenGL Loading Library wiki page, and I have turned to using
glLoadGen more and more recently. It is much easier to understand, and if you ask me, also simpler to use compared to separately building and linking GLEW. This is the reason why SFML is going to get rid of it in favour of a custom loader generator in 2.3 as well and since none of it gets exposed to the user, nobody will have to care about it like they do with GLEW at the moment.