No defenders, per se. 5e is back to more or less the old-school 'fighter wall' or 'meatshield' paradigm: a tough character defends his allies by taking up space - in a corridor, doorway or other choke-point - until he dies. Protection Style and Sentinel help, a little, when you can't do that. Protection Style lets you protect one ally who is adjacent to you once per round (because it's a reaction). Sentinel makes a you a little bit sticky, but also uses your reaction, so you can't do both in the same round. It's not like 3.5 where you could use Reach + Combat Reflexes to lock down a whole section of the battlefield, or 4e where Combat Superiority used an OA but Combat Challenge a reaction. In 5e, it's all (what there is) reactions and you get only 1, so once you've imposed disadvantage on one attack or made an AoO on one enemy, you're done faking 'defender' for the round.
The best way you can draw attacks is to be a 'tank' - tough and high DPR - and hope hitting hard draws attention. That is, fortuitously, exactly what a 5e fighter does, prettymuch by default. You can also try to RP taunting, if your DM goes for that sort of thing. Mostly, your DM is able to have monsters attack whomever they want, so it's a matter of his style whether you watch your allies die a lot, or get beaten down, yourself, more often.