on-call
adjectiveUK /ˌɒnˈkɔːl/
US /ˌɑːnˈkɔːl/
Ready to work or help if someone needs you, even at night or on weekends.
The doctor is on-call tonight, so she keeps her phone close.
OTHER MEANINGS
2. A period of time when someone must be ready to work if needed.
He has an on-call this weekend at the hospital.
3. A person who is ready to help or work when needed.
The on-call nurse answered the phone right away.
4. Available to give help at any time, especially in an emergency.
The plumber offers an on-call service for burst pipes.