Learn Arabic (Modern Standard): المرأة الذكية موظفة.

In Arabic, an adjective must match its noun in definiteness. Because المرأة (the woman) is a specific, definite noun starting with الـ (al-), the adjective describing her must also take الـ. This matching tells us that الذكية (smart) is describing the woman, creating the linked phrase "the smart woman".

Where is the word "is" in this sentence?

Arabic does not use a word for "is" in present tense sentences. The "is" happens naturally between the definite subject (المرأة الذكية, the smart woman) and the indefinite predicate (موظفة, an employee). The jump from a definite phrase to an indefinite noun tells you exactly where the "is" belongs.

How do we know "an employee" (موظفة) is feminine here?

The word ends in the feminine marker taa marbuta (ة). Since the subject is a woman, the noun describing her job must also be feminine to match her gender. If the subject were a man, the word would drop the ة and just be موظف.

The word for "woman" is usually امرأة (imra'a), so why is it spelled المرأة (al-mar'a) here?

The word for "woman" is a special exception in Arabic. When you add the definite article الـ (al-) to امرأة (imra'a), the first letter (alif) drops out completely, changing the spelling to المرأة (al-mar'a). It is one of the very few words that changes its basic shape when made definite.