have at
Upper Intermediate (B2)informal
To attack something or someone, or to tell someone to go ahead and start.
"The two knights circled each other before crying 'have at thee!' and charging forward."
Hear it in context

Lili Reinhart vs. Tom Bateman | Hot Ones Versus
First We Feast · 1:52
Have at it.

1 Hour of Season 5 That Kept the Streak Alive
The Big Bang Theory · 16:32
Have at it.

A Mother-Son Bond Like Mary and Georgie | Young Sheldon Compilation
Young Sheldon · 10:37
Have at it.

What You Can Do in NTE (Neverness To Everness)
GameSpot · 3:15
Have at it.

The Worst Customer at the DMV Pays with PENNIES!? 🤑 DMV | CBS
Comedy Central · 3:42
Have at it.