Tranquil, mainly secure island location in Africa (9)
I believe the answer is:
serengeti
'location in africa' is the definition.
(the Serengeti is a region of Africa)
'tranquil mainly secure island' is the wordplay.
'tranquil' becomes 'serene' (synonyms).
'mainly' means to remove the last letter.
'secure' becomes 'get' (secure can mean to get or obtain).
'island' becomes 'i' (geographical abbreviation).
'serene' with its final letter taken away is 'seren'.
'seren'+'get'+'i'='SERENGETI'
(Other definitions for serengeti that I've seen before include "area of the plain" , "Wildlife-rich region of Africa" , "Tanzanian plain renowned for its wildlife" , "Huge plain in Tanzania" , "African plain noted for wildlife" .)