The unit of meaning is "high on Chennai Super Kings's agenda". Literally, if something is "high on an agenda" then it appears near the top of an agenda (a list of topics to be discussed at a meeting), and so will be discussed early in the meeting, and so by implication is of high importance. Figuratively, there does not need to be an actual written agenda: the idiom just means that the thing (in this case ending the losing streak) is important and needs to be dealt with promptly.
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