The phrase "clashes with" can be replaced with various synonyms, depending on the context. For instance, you may use the term "disagrees with" to indicate a difference of opinion or ideology. If the situation involves a physical altercation, you may use "battles with" or "fights against". In a workplace setting, "conflicts with" or "challenges" may be suitable alternatives. Conversely, you can use "opposes" or "contradicts" when referring to conflicting ideas or beliefs. Other synonyms for "clashes with" include "counters", "contrasts", "contravenes" and "challenges". As a writer or speaker, it is essential to choose the appropriate synonym to effectively convey the intended meaning.