Maroon, thus dead on island (7)
I believe the answer is:
isolate
'maroon' is the definition.
(I've seen this before)
'thus dead on island' is the wordplay.
'thus' becomes 'so' ('so' can be a synonym of 'thus').
'dead' becomes 'late' ('late' can be similar in meaning to 'dead').
'on' means one lot of letters go next to another.
'island' becomes 'i'.
'so'+'late'='solate'
'solate' after 'i' is 'ISOLATE'.
(Other definitions for isolate that I've seen before include "split up" , "Keep apart" , "Pick out" , "Segregate. close off" , "Set apart, quarantine" .)