razbistriti

1. (of one's head, thoughts) to clear one's head; to clear one's mind
   Izašao sam u šetnju da razbistrim glavu. — I went out for a walk to clear my head.
   Posle dobrog sna misli su mi se razbistrile. — After a good sleep my mind cleared.
2. (of a situation, matter) to clarify; to clear up
   Moramo da razbistrimo ovu situaciju pre sastanka. — We need to clear up this situation before the meeting.
   Stvari su se konačno razbistrile. — Things finally became clear.
3. (razbistriti se, of sky, weather) to clear up
   Posle kiše nebo se razbistrilo. — After the rain the sky cleared up.
4. (of a liquid) to make clear; to clarify
   Voda se razbistrila kad se mulj slegao. — The water cleared once the silt settled.

The imperfective is razbistravati; very common in razbistriti glavu / misli.