like a crystal cow in knackerland
Used of something or someone unsuited to a given environment, placed there hopefully for well-intended reasons but left defenceless. From a decision by the relevant authorities in Dublin, Ireland in recent years to mount life-size statues of cows in various media and colours in outdoor locations throughout the centre of the city. The cows were soon vandalised, including one dainty little critter with an elaborate design of cut glass that was left, as you do, in one of the less salubrious areas of the city centre and promptly smashed.
She left little Johnny off at school to face the roughest class in the place, like a crystal cow in knackerland.