Island in March is bliss (8)
I believe the answer is:
paradise
'is bliss' is the definition.
(thesaurus)
'island in march' is the wordplay.
'island' becomes 'is'.
'in' is an insertion indicator.
'march' becomes 'parade' (parading is a kind of marching**).
'is' put into 'parade' is 'PARADISE'.
(Other definitions for paradise that I've seen before include "limbo" , "What was lost to the poet" , "Elysian fields" , "perfect place" , "park" .)