Argument against company name (3)
I believe the answer is:
con
'argument against' is the definition.
(as in pros and cons)
'company name' is the wordplay.
'company' becomes 'co' (abbreviation).
'name' becomes 'n' (common abbreviation e.g. on forms).
'co'+'n'='CON'
(Other definitions for con that I've seen before include "Fleece" , "Dupe" , "Swindle, deception" , "Study - swindle" , "Swindle or see" .)