This is the 642nd most frequent Hungarian word.
derül
"Derül" means "clears up" or "brightens" (often referring to the weather or mood).
In this sentence, 'derül' describes the process of the sky becoming clear, i.e., free of clouds, often used in meteorological context.
Az ég kiderül eső után.
The sky clears after rain.
Here, 'derül' is used metaphorically to indicate that a situation is becoming more understandable or understandable aspects are manifesting.
Végre derül a helyzet.
Finally, the situation becomes clearer.
In this context, 'derül' means to express joy or laughter, often used in relation to something funny or amusing.