ACT - Something done, a deed.
CAT - Any similar animal of the family Felidae, which includes lions, tigers, bobcats, etc.
CUT - Having been cut.
ICY - Pertaining to, resembling, or abounding in ice; cold; frosty.
TAU - The name of the letter T/τ in the Greek, Hebrew and ancient Semitic alphabets, being the nineteenth letter of the Classical and Modern Greek, the twentieth letter of Old and Ancient Greek.
TIC - A local and habitual convulsive motion of certain muscles.
CAY - A small, low island largely made of sand or coral.
CITY - A large settlement, bigger than a town.
ACUITY - Sharpness or acuteness, as of a needle, wit, etc.