Weight carried by this argument after pub (6)
I believe the answer is:
barrow
'weight carried by this' is the definition.
'argument after pub' is the wordplay.
'argument' becomes 'row' (I've seen this before).
'after' says to put letters next to each other.
'pub' becomes 'bar' (I've seen this before).
'row' after 'bar' is 'BARROW'.
(Other definitions for barrow that I've seen before include "Cart for one of the three sisters" , "Handcart; burial mound" , "Northern town" , "Prehistoric burial ground or small cart with wheels" , "such as street-trader might have?" .)