Excuse corrupt Bali island (5)
I believe the answer is:
alibi
'excuse' is the definition.
(alibiing is a kind of excusing)
'corrupt bali island' is the wordplay.
'corrupt' is an anagram indicator.
'island' becomes 'i' (**).
'bali' anagrammed gives 'alib'.
'alib'+'i'='ALIBI'
(Other definitions for alibi that I've seen before include "Legal defence, plea" , "Defence against accusation - was seen elsewhere at the time" , "Excuse, in law" , "that gets him off the hook?" , "Defence in court" .)