Bird spotted in summer — linnet? (6)
I believe the answer is:
merlin
'bird' is the definition.
(merlin is a kind of bird)
'spotted in summer linnet?' is the wordplay.
'spotted in' indicates a hidden word.
'MERLIN' is hidden within 'summer linnet'.
(Other definitions for merlin that I've seen before include "Bird of prey - magician" , "Small falcon; wizard" , "Magician of Arthurian legend" , "King Arthur's magician" , "Kind of hawk or Camelot's magician" .)