Total airhead painting round island (7)
I believe the answer is:
sumatra
'island' is the definition.
(Sumatra is an example)
'total airhead painting round' is the wordplay.
'total' becomes 'sum' (synonyms).
'airhead' becomes 'a' (head letter of 'air').
'painting' becomes 'art' (painting is an art).
'round' is a reversal indicator.
'art' in reverse letter order is 'tra'.
'sum'+'a'+'tra'='SUMATRA'
(Other definitions for sumatra that I've seen before include "Large island of Indonesia" , "Island in western Indonesia" , "part of Indonesia" , "Some land" , "A US mart on an Indonesian island?" .)