The phrase "well in" can refer to something that is deeply ingrained or established in a particular situation or context. There are a number of synonyms that can be used to convey this meaning, including "firmly rooted," "deeply embedded," "entrenched," "ingrained," "pervasive," and "widespread." These words all describe something that is difficult to uproot or change, and that has become a fundamental part of a particular system or way of doing things. When using these words to describe something that is "well in," it is important to consider the context and to choose the word that best fits the tone and meaning of your writing.