Is clean those brass adjectives

Assuming you mean, are the Words "clean those brass" adjectives, the answer is no, maybe, and yes

Clean is a verb.

Those is a demonstrative pronoun. (Some people might call this a form of adjective, as it is a modifier.)

Brass is an adjective: a brass Trumpet, a brass bookend. Note that brass is also a noun in some uses: the brass on that uniform is shiny, the brass in this orchestra is very good