Lean on a good article (5)
I believe the answer is:
thing
'article' is the definition.
(both can mean an object)
'lean on a good' is the wordplay.
'lean' becomes 'thin' (associated in meaning).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'a good' becomes 'g' (abbreviation).
'thin'+'g'='THING'
(Other definitions for thing that I've seen before include "cup of tea" , "Affair - matter" , "See 1" , "Individual unit" , "Unspecified object" .)