Among the partisans I detected bias (4)
I believe the answer is:
side
'bias' is the definition.
(as in being one-sided)
'among the partisans i detected' is the wordplay.
'among' indicates a hidden word.
'SIDE' can be found hidden inside 'partisans i detected'.
(Other definitions for side that I've seen before include "Pomposity - bias - team" , "Affectation" , "Team - arrogance" , "Spin given to a ball by striking it off-centre" , "part" .)