How to care for a poor quality nuc:
A nuc should contain a queen and at least 2 frames brood, about 2 frames honey and pollen stores, and the 5th frame is supplier’s choice, possibly empty, even blank without drawn comb. There should be enough bees to cover or work all frames.
If you have received a substandard nuc, one containing fewer bees or resources, boost and protect that colony to prevent its failure. If you have other healthy hives or another well-stocked nuc that can spare even a little brood and resources, transfer some. A frame of capped brood will emerge and quickly boost the workforce of the weak colony. Open brood will stop the colony from hunger “swarming” which is actually a form of absconding. Such a stressed colony faces the “No food, no brood, let’s fly and try elsewhere" decision to abscond. Even empty drawn comb transferred in is a boost to a stressed weak colony.
Feed 1:1 sugar:water and pollen sub patty placed on top of the brood frames without stopping until colony strength comes up to standard. Use a robbing screen (better than merely reducing size of the entrance) to protect this weak colony from vespids and stronger bee colonies, even another nuc close by that is standard strength.
In short, do everything you can to boost and protect and then rely on the natural resilience of Apis mellifera, a resilience built up by millions of years of development, in the creation of this amazing species.