This is the 4648th most frequent German word.
ungeklärter
"Unresolved" or "unsolved."
Here, 'ungeklärter' is used as an adjective describing 'Fall'. It means 'unresolved' or 'not clarified'.
Die Polizei untersucht einen ungeklärten Fall.
The police are investigating an unresolved case.
The word 'ungeklärt' is used here in its adjective form to describe 'Fragen', conveying the sense of 'not clarified or solved'.
Einige Fragen bleiben ungeklärt.
Some questions remain unresolved.
In this sentence, 'ungeklärte' is showing its adjectival usage and describes 'Sachverhalte' as matters that are unresolved or unclear.