Some problems — we argue and use bad language (5)
I believe the answer is:
swear
'use bad language' is the definition.
(I've seen this before)
'some problems we argue' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SWEAR' is hidden within 'problems we argue'.
'and' acts as a link.
(Other definitions for swear that I've seen before include "Affirm" , "Eff and blind" , "Promise on oath" , "Assert" , "Vow; blaspheme" .)