Leading old African general returning from America (5)
I believe the answer is:
negus
'leading old african' is the definition.
(term for king in some historical African kingdoms)
'general returning from america' is the wordplay.
'general' becomes 'gen'.
'returning' says the letters should be written in reverse.
'from america' becomes 'US'.
'gen' written backwards gives 'neg'.
'neg'+'us'='NEGUS'
(Other definitions for negus that I've seen before include "Abyssinian king - hot, spicy drink" , "Abyssinian king - spiced drink" , "Old Ethiopian king; hot port drink" , "Hot stimulant" , "Ethiopian emperor (hist.)" .)