He is biased in favour of a member of the resistance movement (8)
I believe the answer is:
partisan
'he is biased' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'in favour of a member of the resistance movement' is the wordplay.
'in' indicates putting letters inside.
'favour of a member of' becomes 'paisan' (I can't explain this - if you can you should give a lot more credence to this answer).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'resistance' becomes 'r' (electronics abbreviation).
'movement' indicates an anagram (letters move around).
't'+'r'='tr'
'tr' with letters rearranged gives 'rt'.
'paisan' going around 'rt' is 'PARTISAN'.
Can you help me to learn more?
(Other definitions for partisan that I've seen before include "Prejudiced towards one cause" , "Inclining to one side" , "Prejudiced towards a particular cause" , "Prejudiced in favour of a particular cause" , "Guerrilla" .)