Extremism very much on track under extreme characters in Zimbabwe (8)

I believe the answer is:

zealotry

I'm a little stuck... Click here to teach me more about this clue!

'extremism' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for zealotry that I've seen before include "Keenness" , "Extremism" , "Fanaticism" , "Excessive devotion" , "Passionate religious feeling" .)

I've seen this clue in The Telegraph.

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