Omen still represented heavy burden (9)
I believe the answer is:
millstone
'heavy burden' is the definition.
(I've seen this before)
'omen still represented' is the wordplay.
'represented' indicates anagramming the letters.
'omen'+'still'='omenstill'
'omenstill' anagrammed gives 'MILLSTONE'.
(Other definitions for millstone that I've seen before include "something hard to bear" , "Heavy burden" , "Grinding disc; wearisome burden" , "Heavy and inescapable responsibility" .)