Be sufficient for arguing, tho, every so often (3,2)
I believe the answer is:
run to
'be sufficient for' is the definition.
(run or last to the requirement amount)
'arguing tho every so often' is the wordplay.
'every so often' means one should take alternating letters.
'arguing'+'tho'='arguingtho'
The alternate letters of 'arguingtho' are 'RUN TO'.
(Other definitions for run to that I've seen before include "Reach" , "Have enough" , "Be sufficient for (eg, the purchase of something)" , "Afford" .)