African nation importing fifth of sugar beet (5)
I believe the answer is:
chard
'beet' is the definition.
(chard is a kind of beet)
'african nation importing fifth of sugar' is the wordplay.
'african nation' becomes 'Chad' (country in Africa).
'importing' is an insertion indicator.
'fifth of sugar' becomes 'r' (5th letter of 'sugar').
'chad' going around 'r' is 'CHARD'.
(Other definitions for chard that I've seen before include "Leafy green" , "vegetable crop" , "Beet with edible leaves and stalks" , "Variety of beet with edible leaves" , "Green vegetable" .)