Crossword Clue:

to warn beforehand

AnswerCrossword Clue
MONITORIALServing to warn.
FOREStart to warn
ORELSEWords to warn you
SEAMARKSBeacons to warn mariners.
GALEReason to warn boaters
BELLDevice to warn mice of cats.
KNOCKDOWNPITCHHurler's strategy to warn the hitter
THEBOGEYMANWhat a parent might warn a child to watch out for