Is ONE PIECE episode 607 filler?
Canon No, episode 607 of ONE PIECE is canon.
#607
A Fierce Battle Gets Heated! Luffy vs. Caesar!
白熱の激戦 ルフィＶＳシーザー
Aired 11 Aug 2013
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.