that's not too bad of a crack. you might be able to sane it down (i.e. remove the rough/loose edges) and brush on some kind of clear fiberglass resin. it would not fix the crack, but you could @ least do that and blend out into the clear. hit it w/ some cheap clear, wet sand it w/ like 1500-2000 grit wet/dry paper, and buff it out w/ a buffer. it should look much better, and you'd only notice it if you were up close and (prolly) looknig for the crack