It means for you to keep your hat. Perhaps you are thinking of "keep this under your hat," which means "keep it to yourself" or "keep it secret." The image is of someone hiding something beneath their hat, on top of their head, where only they know it's there.
Literally, this is going to be a fast, rough ride and your hat will blow off if you don't hang on to it. Figuratively, we're going to do something fast with few precautions.
aldwme
banana
In a rebus, "ecnalg" is "a backward glance".
To keep something under your hat means to keep it hidden.It means don't tell anyone -- keep the news to yourself.Don't need to advertise. Be casually discrete; just keep "it" with you (so to speak). And go about your way.
crossroads
missing you
Missing you
Dr. Doolittle
Mad about you?
Mmm