Dreary poet making comeback (4)
I believe the answer is:
drab
'dreary' is the definition.
(synonyms)
'poet making comeback' is the wordplay.
'poet' becomes 'bard' (bard is a kind of poet).
'making comeback' says the letters should be written in reverse.
'bard' reversed gives 'DRAB'.
(Other definitions for drab that I've seen before include "Dull-brown" , "Cheerless, shabby" , "Drearily dull; slattern" , "Of a dull greenish-brown colour" , "Dull and boring" .)