Uninformed, partial, malign or antagonistic (8)
I believe the answer is:
ignorant
'uninformed' is the definition.
(I know that uninformed can be written as ignorant)
'partial malign or antagonistic' is the wordplay.
'partial' indicates a hidden word.
'IGNORANT' can be found hidden inside 'malign or antagonistic'.
(Other definitions for ignorant that I've seen before include "Unknowing" , "Lacking in education" , "Unlearned, lacking knowledge" , "Knowing nothing" , "Lacking information" .)