'A', for instance may be six-time African despot (7)
I believe the answer is:
vitamin
'a for instance' is the definition.
(I know that A is a type of fat-soluble vitamin)
'six-time african despot' is the wordplay.
'six' becomes 'VI' (Roman numerals).
'time' becomes 't' (abbreviation).
'african despot' becomes 'Amin' (Ugandan dictator Idi Amin).
'vi'+'t'+'amin'='VITAMIN'
'may be' acts as a link.
(Other definitions for vitamin that I've seen before include "Substance aiding metabolism" , "Essential diet compound" , "Natural organic substance essential to health" , "A, B, C, D, E or K" , "Organic substance essential to life" .)