Work with pretending to be on the other side (8)
I believe the answer is:
opposing
'be on the other side' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I don't see?
'work with pretending' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'with' is a charade indicator (letters next to each other).
'pretending' becomes 'posing' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'op'+'posing'='OPPOSING'
'to' is the link.
Can you help me to learn more?
(Other definitions for opposing that I've seen before include "Contending" , "Disapproving" , "Going against" , "trying to end a sea of troubles by it?" , "modelling after work" .)