Viceroy's South American gin (6)
I believe the answer is:
satrap
'viceroy's' is the definition.
(thesaurus)
'south american gin' is the wordplay.
'south american' becomes 'SA'.
'gin' becomes 'trap' (I've seen this before).
'sa'+'trap'='SATRAP'
(Other definitions for satrap that I've seen before include "Sparta (anag.)" , "A sprat for the old governor of Persia" , "Persian provincial governor" , "Old head" , "Old Persian governor - a sprat (anag)" .)