Some media covering party bias (10)
I believe the answer is:
prepossess
'bias' is the definition.
(I know that bias is a kind of prepossess)
'some media covering' is the wordplay.
'some' becomes 'posse' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'media' becomes 'press' (the press is part of the media).
'covering' is an insertion indicator.
'posse' placed into 'press' is 'PREPOSSESS'.
'party' is the link.
Can you help me to learn more?
(Other definitions for prepossess that I've seen before include "Influence" , "Bias favourably" .)