Argue about pound coins (5)
I believe the answer is:
clash
'argue' is the definition.
(thesaurus)
'about pound coins' is the wordplay.
'about' means one lot of letters goes inside another.
'pound' becomes 'l'.
'coins' becomes 'cash' (I've seen this before).
'l' put into 'cash' is 'CLASH'.
(Other definitions for clash that I've seen before include "Forceful disagreement" , "Come together discordantly" , "Disagree violently" , "Come into violent conflict" , "Fail to fit" .)