Dreary poet sent up (4)
I believe the answer is:
drab
'dreary' is the definition.
('drab' can be a synonym of 'dreary')
'poet sent up' is the wordplay.
'poet' becomes 'bard' (bard is a kind of poet).
'sent up' is a reversal indicator.
'bard' written backwards gives 'DRAB'.
(Other definitions for drab that I've seen before include "Dull and monotonous" , "Dull - dreary" , "kind of tart" , "Shabby; a slattern (arch.)" , "Cheerless, shabby" .)