Answer: tunneled

AnswerCrossword Clue
TUNNELED

Made like a mole

TUNNELED

Worked underground

TUNNELED

Went underground

TUNNELED
Burrowed.
TUNNELED
Dug, as a sand hog.
TUNNELEDBuilt subways.
TUNNELEDBored
TUNNELEDBurrowed
TUNNELEDMade an aqueduct, maybe
TUNNELEDEmulated a mole