Petty article by this writer (4)
I believe the answer is:
mean
'petty' is the definition.
(thesaurus)
'article by this writer' is the wordplay.
'article' becomes 'an' (indefinite article).
'by' means one lot of letters go next to another.
'this writer' becomes 'me' (the person who is writing these clues).
'an' after 'me' is 'MEAN'.
(Other definitions for mean that I've seen before include "Niggardly" , "Stand for - penny-pinching" , "spell" , "Spiteful -- excellent (slang)" , "Intend - shabby" .)