Eastern play about small island (4)
I believe the answer is:
eyot
'small island' is the definition.
(I've seen this before)
'eastern play about' is the wordplay.
'eastern' becomes 'e'.
'play' becomes 'toy' (synonyms).
'about' shows that the letters should be reversed in order.
'toy' written backwards gives 'yot'.
'e'+'yot'='EYOT'
(Other definitions for eyot that I've seen before include "Another term for ait" , "Small river island" , "Islet found in a river, (especially in England)" , "There's one at Chiswick" , "land in the river" .)