Something that is subcurative is not fully able to cure a disease or illness, but it can help a little bit.
Subcurative things are not strong enough to cure, but they can still be helpful.
Examples:
The medicine is subcurative, so it won't make you all better, but it might help a little.
The subcurative treatment didn't make her completely well, but she felt a little better.
The subcurative therapy didn't work as well as they hoped.
The subcurative potion didn't work, but it did make the wizard's nose turn blue!
The subcurative spell only made the frog's warts a little smaller.
The subcurative bandage didn't heal the cut, but it stopped the bleeding a little.