Small island turning black (5)
I believe the answer is:
sable
'black' is the definition.
(heraldic term for black)
'small island turning' is the wordplay.
I cannot quite see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found in the answer.
The remaining letters 'able' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sable that I've seen before include "Type of fur" , "North Asian marten" , "Bales of valuable Russian fur" , "Antelope, fur" , "fur coat" .)