Something hooted on top of Ray’s tree (8)
I believe the answer is:
hornbeam
'tree' is the definition.
(type of tree)
'something hooted on top of ray's' is the wordplay.
'something hooted' becomes 'horn' (eg you might hoot a car horn).
'on top of' means one lot of letters go next to another.
'ray' becomes 'beam' (synonyms).
'horn'+'beam'='HORNBEAM'
(Other definitions for hornbeam that I've seen before include "Resident in wood perhaps" , "is found in wood" , "heavy plant" , "Timber" , "Tree good for hedging" .)