fly in the ointment(n = noun.attribute) - an inconvenience that detracts from the usefulness of something;
is a kind of inconvenience, troublesomeness, worriment

alder fly, american fly honeysuckle, antlion fly, bar fly, bee fly, berna fly, black fly, blow fly, breeze fly, bull fly, burrel fly, caddice fly, caddis fly, canker fly, chalcid fly, chalcis fly, columbatz fly, crane fly, deer fly fever, dobson fly, dry fly, european fly honeysuckle, fish fly, flesh fly, fly, fly agaric, fly amanita, fly ash, fly ball, fly blind, fly bridge, fly by, fly casting, fly contact, fly front, fly fungus, fly high, fly honeysuckle, fly in the face of, fly in the teeth of, fly off the handle, fly on, fly open, fly orchid, fly poison, fly rod, fly sheet, fly tent, fly the coop, fruit fly, golden-eyed fly, greenbottle fly, hanging fly, harvest fly, hemerobiid fly, hessian fly, horn fly, horse fly, house fly, ichneumon fly, lacewing fly, lantern fly, let fly, let fly at, long fly, louse fly, mediterranean fruit fly, mercurial ointment, ointment, on the fly, pomace fly, pop fly, robber fly, sacrifice fly, sand fly, scorpion fly, shoo fly, spanish fly, stink fly, stone fly, streamer fly, swamp fly honeysuckle, syrphus fly, tachina fly, test fly, tsetse fly, tzetze (or tsetse) fly, tzetze fly, vinegar fly, warble fly, warega fly, wet fly, white fly, zinc ointment