Answer:

flea

Answer	Crossword Clue
FLEA	Dog's hitchhiker
FLEA	Canine hanger-on
FLEA	Kind of market

FLEA	Bloodsucking insect
FLEA	Collar kind
FLEA	Doghouse denizen
FLEA	Collar or circus
FLEA	It can be a market or a circus
FLEA	Torment for Fido
FLEA	Discount market
FLEA	Bassist on "Under the Bridge"

FLEA	Pitbull biter, say
FLEA	Pet peeve
FLEA	Dog biter
FLEA	Itty-bitty biter
FLEA	Red Hot Chili Peppers bassist
FLEA	Abominable hopper
FLEA	Biter of a boxer?
FLEA	Fido annoyer

FLEA	Type of market
FLEA	Fido rider?
FLEA	High jumper
FLEA	Wingless insect
FLEA	Bloodsucking bug
FLEA	Bug with bounce
FLEA	Dog's bane
FLEA	Spot on Spot, maybe

FLEA	Bug on a dog
FLEA	Little hopper
FLEA	Boxer's bane
FLEA	Kind of market or circus
FLEA	Pet pest
FLEA	Insect in the order Siphonaptera
FLEA	Bomb target
FLEA	Critter known for its leaping ability

FLEA	One might make Spot scratch
FLEA	Dog collar target
FLEA	Circus leaper
FLEA	Insect in a circus
FLEA	Dog bugger