step into the breach
US /stɛp ˈɪntu ðə briːtʃ/
UK /stɛp ˈɪntu ðə briːtʃ/
1.
to take action when another person or group is unable to, or to fill a gap in a difficult situation
:
•
When the lead actor fell ill, his understudy had to step into the breach.
•
The volunteers had to step into the breach when the regular staff went on strike.