In Portuguese, a can be the feminine singular definite article, so here it means the.
So:
Because jante is a feminine noun, it takes a.
Because adjectives in Portuguese usually agree in gender and number with the noun they describe.
Since jante is feminine singular, the adjective must also be feminine singular:
So:
Portuguese often uses estar for a state or condition, especially one that can change, and ser for something more permanent or defining.
Here, clean is treated as a current condition, so estar is the natural choice:
Using ser here would sound unusual in normal speech, because being clean is not seen as a permanent characteristic of the rim.
In European Portuguese, jante usually means the rim or wheel rim, especially of a car.
It is different from:
In everyday speech, people may sometimes use jante in contexts where English speakers might loosely think of the visible metal part of the wheel.
A careful European Portuguese pronunciation is approximately:
a ZHAN-tuh shtah LEEM-pah
A few useful points:
A more phonetic version would be roughly [ɐ ˈʒɐ̃.tɨ ʃˈta ˈlĩ.pɐ] in European Portuguese.
The plural is:
As jantes estão limpas.
Each part changes to match the plural:
This shows how Portuguese makes articles, nouns, verbs, and adjectives work together.