I defame a Sicilian perhaps (8)
I believe the answer is:
islander
'a sicilian perhaps' is the definition.
(Sicily is an island)
'i defame' is the wordplay.
'defame' becomes 'slander' (synonyms).
'i'+'slander'='ISLANDER'
(Other definitions for islander that I've seen before include "I snarled at one surrounded by water" , "E.g. Shetland inhabitant" , "Rum person perhaps" , "One from Islay, Man, etc" , "Perhaps Sardinian" .)