Lacklustre Eisteddfod winner retired (4)
I believe the answer is:
drab
'lacklustre' is the definition.
(thesaurus)
'eisteddfod winner retired' is the wordplay.
'eisteddfod winner' becomes 'bard' (I've seen this before).
'retired' 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 "Dreary and colourless" , "Colourless like bard" , "Gloomy" , "Rather dull" , "Cheerless, colourless" .)