Summits on colonial hills and dales in Africa (4)

I believe the answer is:

chad

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'in africa' is the definition.
('Chad' is part of 'africa')

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

(Other definitions for chad that I've seen before include "foreign land" , "N.Central African Republic" , "African country and lake" , "North central African country, capital N'Djamena" , "African country south of Libya" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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