Answer: ONTHEQT

AnswerCrossword Clue
ONTHEQTWithout telling anyone
ONTHEQTIn secret
ONTHEQTSecretly
ONTHEQTIn secret: Slang.
ONTHEQTQuietly: Colloq.
ONTHEQTSub rosa
ONTHEQTNot openly
ONTHEQTWithout anyone knowing
ONTHEQTCovertly
ONTHEQTPrivately
ONTHEQTHush-hush
ONTHEQTConfidentially