English play about small island (4)
I believe the answer is:
Here is my best explanation:
'small island' is the definition.
(I've seen this before)
'english play about' is the subsidiary indication.
'english' becomes 'e' (abbreviation).
'play' becomes 'toy' ('toy' can be a synonym of 'play'**).
'about' shows that the letters should be reversed in order.
'toy' in reverse letter order is 'yot'.
(Other definitions for eyot that I've seen before include "land in the river", "River island", "Little island in a river or lake", "isle", "Small river island", "Ait", "small island", "Islet found in a river, (especially in England)", "Fawlty Towers waiter" and "There's one at Chiswick".)