The new track follows up on the previously revealed 'The Only Heartbreaker' and 'Working for the Knife'.
There's also Bring Me The Horizon, Rage Against The Machine, Wolf Alice, Glass Animals, Bastille, Fontaines DC, Run The Jewels and loads more.
The London festival is now set to take place across two days.
Talking about the track, lead singer Lydia Night says: “It's the first time I've ever written directly about a girl I had a crush on."
It's the sixth video to come from most recent album 'Happier Than Ever'.
Support across the run will come from a mix of Waxahatchee, Princess Nokia, Faye Webster, Sasami and Buzzy Lee.
It's on air tonight (Monday 6th December) from 8pm GMT.
The pair are teaming up for a strong of dates next June and July.
Tickets go on sale this Friday, 10th December.
Also Black Midi, Ghetts, SG Lewis and 'others'.