One phrase, 2 meanings. Learn them one at a time, then test yourself.
Meaning 1 · most common
To increase your effort, activity, production, or pressure when more is needed.
Example
A: We're getting way more orders than last month.
B: Then we'll have to step up production, or we'll fall behind.
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Meaning 2
To step up means to take responsibility and act when help or leadership is needed.
Example
A: Who's going to lead the project?
B: Tom stepped up when nobody else offered.
Tell it apart
Read the sentence, then pick the meaning that's in play.
Pick a meaning and say it out loud. Save the ones you mix up.