Old African island supported by Scotsman (9)
I believe the answer is:
rhodesian
'old african' is the definition.
(I've seen this before)
'island supported by scotsman' is the wordplay.
'island' becomes 'Rhodes' (Greek island).
'supported by' means one lot of letters go next to another (in a down clue, some letters hold up others).
'scotsman' becomes 'ian' (common Scottish name).
'rhodes'+'ian'='RHODESIAN'
(Other definitions for rhodesian that I've seen before include "Large dog (from Zambia or Zimbabwe?)" , "Zimbabwean, 1964-79" , "Citizen of pre-Zimbabwe state - thus he ordains" , "old African" , "old countryman" .)