How can Allah Almighty say in the Noble Quran that it is in a "clear Arabic tongue," yet we find differences in interpretations among linguists, and does that mean the Quran is unclear?

There is no contradiction between the Quran being revealed in a clear Arabic tongue and the differing interpretations of some of its words by exegetes. This is because the nature of the Arabic language includes homographs and synonyms, and this possibility of multiple meanings is part of the Quran's miraculousness. Ibn Juzayy mentioned twelve reasons for the differences among exegetes, including: differences within the Quran itself, differences in grammatical constructions, differences among linguists regarding the meaning of a word, a word having multiple meanings (homonymy), the possibility of a general or specific meaning, the possibility of an absolute or restricted meaning, the possibility of a literal or metaphorical meaning, the possibility of an implied word, the possibility of an extra word, the possibility of order or inversion (precedence and delay), the possibility of abrogation and firm establishment, and differing narrations from the Prophet and the Salaf.