Answer: piggybacked

AnswerCrossword Clue
piggybackedCarry by or as if by piggyback
piggybackedMount on or attach to (an existing object or system)
piggybackedUse existing work or an existing product as a basis or support
piggybackedPIGGYBACK, to carry someone on one's back also PICKABACK, PICKAPACK, PICKBACK