Dull poet on the rise (4)
I believe the answer is:
drab
'dull' is the definition.
(similar in meaning)
'poet on the rise' is the wordplay.
'poet' becomes 'bard' (bard is a kind of poet).
'on the rise' says the letters should be written in reverse (in a down clue, letters go up).
'bard' back-to-front is 'DRAB'.
(Other definitions for drab that I've seen before include "Cheerless, shabby" , "Dull - dreary" , "Colourless like bard" , "Drearily dull; slattern" , "Dull sort of bard" .)