Flipping Shakespeare's boring! (4)
I believe the answer is:
drab
'boring' is the definition.
(thesaurus)
'flipping shakespeare's' is the wordplay.
'flipping' says the letters should be written backwards.
'shakespeare' becomes 'bard' (I've seen this before).
'bard' back-to-front is 'DRAB'.
(Other definitions for drab that I've seen before include "Dismal < slattern" , "Dull, uninteresting" , "Dingy, dull" , "Dull sort of bard" , "kind of tart" .)