Island's prosperity assured by militant organisation (7)
I believe the answer is:
madeira
'island's' is the definition.
(I've seen this before)
'prosperity assured by militant organisation' is the wordplay.
I cannot really understand how this works, but
'organisation' could be 'ira' (I have seen 'Illegal organisation ' mean 'ira' so perhaps 'organisation' could also mean 'ira') and 'ira' is located in the answer.
The remaining letters 'made' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for madeira that I've seen before include "Dessert wine from a Portuguese Atlantic island" , "Island in the Atlantic Ocean" , "Atlantic island, famed for its sweet wine" , "Portuguese island off northwest Africa" , "Fortified white wine from island off NW Africa" .)