Shakespeare is flipping tedious (4)
I believe the answer is:
bard
'shakespeare' is the definition.
(I've seen this before)
'flipping tedious' is the wordplay.
'flipping' says the letters should be written backwards.
'tedious' becomes 'drab' (I've seen this before).
'drab' written backwards gives 'BARD'.
'is' is the link.
(Other definitions for bard that I've seen before include "Eisteddfod winner" , "Animal; cruel person" , "A drab sort of old poet" , "A lyric poet" , "Traditional poet" .)