Dull poet taken up (4)
I believe the answer is:
drab
'dull' is the definition.
(similar in meaning)
'poet taken up' is the wordplay.
'poet' becomes 'bard' (bard is a kind of poet).
'taken up' is a reversal indicator.
'bard' reversed gives 'DRAB'.
(Other definitions for drab that I've seen before include "Dull sort of bard" , "Cheerless, shabby" , "kind of tart" , "Dull and monotonous" , "Cheerless, colourless" .)