There are several synonyms for the phrase "stand by," which means to remain available to help or support someone or to be ready to take action when needed. One common synonym is "support," which means to assist or back someone up. Another synonym is "be there," which signifies being present and ready to offer aid. "Stick around" is another way of expressing that one is willing to wait or remain on standby. "Stay near" can also be used to convey that one is ready to provide assistance or help. Finally, the phrase "keep close" can be used to indicate that someone is staying nearby to offer support or help if needed.