Zend certified PHP/Magento developer

_extend.less doesn’t seem to work

I’m trying to add a bit of CSS onto an already existing theme which turns the price classes descended from special-price classes red.

.special-price .price {
    color: red !important;
}

This is in a file called _special_price.less, which is imported into the _extend.less file.

@import '_special_price.less';

It is my understanding that
_extend is compiled last, which means any existing CSS is overwritten, but this doesn’t seem to be happening, as the expected change is absent.

I have flushed and cleaned the cache, compiled, deployed, anything I can think of. Can anyone help?