A compound represented by formula (1), a liquid crystal composition to which the compound is added, and a liquid crystal display device containing the composition. In formula (1), R1 is hydrogen or alkyl having 1 to 20 carbons, or the like; R2 and R3 are independently methyl, ethyl, isopropyl, or t-butyl; ring A is 1,4-cyclohexylene, 1,4-phenylene or the like; Z is a single bond or alkylene having 1 to 6 carbons, or the like; and m is 0, 1, or 2.