Two rugby players back argument (6,3)
I believe the answer is:
second row
'two rugby players' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'back argument' is the wordplay.
'back' becomes 'second' (both can mean to support an idea or proposal).
'argument' becomes 'row' (to row is to argue).
'second'+'row'='SECOND ROW'
Can you help me to learn more?
(Other definitions for second row that I've seen before include "forward line" , "Rugby forwards" , "rugby players" .)