Compound in Zaire’s interior (5)
I believe the answer is:
resin
'compound' is the definition.
(resin is a kind of compound)
'in zaire's interior' is the wordplay.
'in' indicates a hidden word.
'RESIN' can be found hidden inside 'zaires interior'.
(Other definitions for resin that I've seen before include "Sap product" , "Sticky stuff for siren" , "Sticky substance exuded by pine trees" , "Substance produced from sap of some plants and trees" , "Glue" .)