1. A split or division: This is the most common meaning. A cleft can be a physical split in something, like a cleft palate (a split in the roof of the mouth) or a cleft chin (a split in the chin). It can also refer to a metaphorical split or division, such as a cleft in the rock (a crack in the rock) or a cleft in their relationship (a division or disagreement).
2. A narrow valley: This meaning is less common, but it is still valid. A cleft can refer to a narrow, steep-sided valley, often formed by erosion.
3. A part of a word: This is the least common meaning. A cleft can be a part of a word that is split off from the main word, as in the phrase "cleft palate."
In general, the meaning of "cleft" will be clear from the context. If you are unsure, it is always best to ask for clarification.