Article is by member, not us (4)
I believe the answer is:
them
'not us' is the definition.
(I've seen this before)
'article is by member' is the wordplay.
'article' becomes 'the' (the definite article in English).
'is by' means one lot of letters go next to another.
'member' becomes 'm' (political abbreviation).
'the'+'m'='THEM'
(Other definitions for them that I've seen before include "Let -- eat cake" , "... in another case, they" , "Perhaps, the Opposition" , "Those people (as object)" , "people objectively" .)