It’s rolled perfectly – let’s have no arguments! (5,4)
I believe the answer is:
thats flat
'rolled perfectly let's have no arguments' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'it's' is the wordplay.
I cannot quite see how this works, but
'it's' could be 'ts' (abbreviation. e.g. in 'tis) and 'ts' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for thats flat that I've seen before include "there's nothing more to be said" , "There's no argument" , "lacks sparkle" , "... may provoke this criticism" , "Informally, it's quite definite - or horizontal?" .)