Dreary Shakespeare sent up (4)
I believe the answer is:
drab
'dreary' is the definition.
(synonyms)
'shakespeare sent up' is the wordplay.
'shakespeare' becomes 'bard' (I've seen this in another clue).
'sent up' says the letters should be written in reverse.
'bard' in reverse letter order is 'DRAB'.
(Other definitions for drab that I've seen before include "Dull and monotonous" , "Dull, uninteresting" , "Drearily dull; slattern" , "Sombre" , "Dismal < slattern" .)