The phrase "light on" generally refers to something that is lacking in a certain area or aspect. However, there are several other synonyms that can be used to convey a similar meaning. For instance, the phrase "scarce on" can be used in place of "light on," particularly when referring to a shortage of resources or supplies. "Deficient in" is another possible synonym, which implies a deficiency or inadequacy in a particular area. Other synonyms include "sparse in," "meagre on," and "short on." These words are all useful in conveying a sense of something being insufficient or lacking, without directly using the word "light on".