Disturbed thrushes etc, on tree (5,8)
I believe the answer is:
horse chestnut
'tree' is the definition.
(horse-chestnut is a kind of tree)
'disturbed thrushes etc on' is the wordplay.
'disturbed' indicates an anagram.
'thrushes'+'etc'+'on'='thrushesetcon'
'thrushesetcon' with letters rearranged gives 'HORSE-CHESTNUT'.
(Other definitions for horse chestnut that I've seen before include "Source of timber" , "whose shade may be seen in park" , "Tree with sticky buds" , "Tree with conkers" , "It bears fruit" .)