Answer: mules

AnswerCrossword Clue
MULESCotton-spinning machines
MULESDrug smugglers
MULESObstinate ones
MULESPlow pullers
MULESSymbols of stubbornness
MULESSlippers for the stubborn?
MULESBeasts of burden
MULESHybrid animals
MULESSlip-ons
MULESSterile hybrids
MULESFarm animals
MULESCertain slippers
MULESFancy footwear
MULESHybrid critters
MULESClogs or beasts
MULESBalky ones
MULESFootwear
MULESMoscow ... (vodka drinks)
MULESOpen-back shoes
MULESSlippers of sorts
MULESSome slippers
MULESGov't and Waits' "Variations"
MULESAl Stewart might travel with "Three"
MULESStubborn critters
MULESStubborn creatures
MULESPack animals
MULESStrapless slippers
MULESEquine hybrids
MULESCanyon transports
MULESTeam mates
MULESContraband carriers
mulesthe offspring of a donkey and a mare
mulesto remove anal wrinkles of a sheep to prevent flystrike
MULESWagon-train team
MULESSlippers
MULESStubborn beasts
MULESLounging slippers
MULESLounging wear
MULESStubborn sorts
MULESBurros' relatives