This is the 4392nd most frequent Arabic word.
واضحا
Clear or obvious.
The word 'واضحا' describes the clarity of the matter, acting as a predicate in this context to provide descriptive information about the situation.
الأمر واضحا للجميع.
The matter is clear to everyone.
Here 'واضحا' (as واضحة matching the feminine form for 'طريقة') is used as an adjective to describe the manner in which the teacher explained.
شرح المعلم الدرس بطريقة واضحة.
The teacher explained the lesson in a clear manner.
In this example, 'واضحا' functions as a predicate adjective to describe the subject ('he') in terms of being clear in expression.