Tipped off (4)
'tipped off' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for alerted that I've seen before include "Altered, having been put on guard" , "Warned or aroused to a sense of danger" , "Given warning" , "Put on guard, warned" , "Related about warning notified" .)
'tipped off' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for told that I've seen before include "Related (a story)" , "Informed; narrated" , "instructed" , "Made an impact" , "Said" .)