tip somebody off about something

Từ điển Oxford Advanced Learner 8th

ˌtip sbˈoff (about sth) derived
(informal)to warn sb about sth that is going to happen, especially sth illegal
•Three men were arrested after police were tipped off about the raid.
•~ that… They were tipped off that he might be living in Wales.
related noun ↑tip-off
Main entry: ↑tip_derived