wait in the wings
US /weɪt ɪn ðə wɪŋz/
UK /weɪt ɪn ðə wɪŋz/
1.
to be ready to do something or to take someone's place, especially in a play or other performance
:
•
The understudy is waiting in the wings, ready to perform if the main actor falls ill.
•
There are several talented young players waiting in the wings for a chance to join the first team.