Answer: rubadubdub

AnswerCrossword Clue
RUBADUBDUBNursery rhyme intro
RUBADUBDUBStart of a nursery rhyme
RUBADUBDUBStart of a rhyme featuring a butcher and baker
RUBADUBDUBNursery-rhyme sound
RUBADUBDUBNursery rhyme starter
RUBADUBDUBFirst line of a nursery rhyme
RUBADUBDUBCertain nursery rhyme intro