You are silly backing socialist (6)
I believe the answer is:
reader
'you' is the definition.
(I've seen this before)
'silly backing socialist' is the wordplay.
'silly' becomes 'rea' (I can't justify this - if you can you should believe this answer much more).
'backing' is a reversal indicator.
'socialist' becomes 'red' (red can informally mean a socialist).
'red' in reverse letter order is 'der'.
'rea'+'der'='READER'
'are' acts as a link.
Can you help me to learn more?
(Other definitions for reader that I've seen before include "One who studies - or his book" , "See 15" , "University lecturer - text book" , "Learning book" , "One perusing book" .)