Tree spotted with extremities eaten away (5)
I believe the answer is:
apple
'tree' is the definition.
(apple is a kind of tree)
'spotted with extremities eaten away' is the wordplay.
'spotted' becomes 'dappled' (dappling is a kind of spotting).
'with extremities eaten away' means to look at the middle letters.
The middle letters of 'dappled' are 'APPLE'.
(Other definitions for apple that I've seen before include "Adam had one!" , "something to eat" , "Pupil" , "Granny Smith, for one" , "Dressing; Irish county" .)