step up

Ellipsis of step up to the plate (“take one's turn at bat, take responsibility”).

• "Won't anyone step up to the challenge?"
• "The Gunners continued to press after the break but it was Leeds who broke the deadlock in the 54th minute. There was no doubt about the penalty either, with Denilson clumsily fouling Gradel and Snodgrass stepping up to find the bottom corner of the net."

• volunteer
• offer

• step aside
• step down