Taxing dumber ones works (10)
I believe the answer is:
burdensome
'taxing' is the definition.
(synonyms)
'dumber ones works' is the wordplay.
'works' indicates anagramming the letters (work can mean to twist or convulse).
'dumber'+'ones'='dumberones'
'dumberones' is an anagram of 'BURDENSOME'.
(Other definitions for burdensome that I've seen before include "Onerous" , "Oppressive, wearisome" .)