Counter-argument later changed to accommodate objection (8)
I believe the answer is:
rebuttal
'counter-argument' is the definition.
(I've seen this before)
'later changed to accommodate objection' is the wordplay.
'changed' indicates an anagram.
'to accommodate' means one lot of letters goes inside another.
'objection' becomes 'but'.
'later' is an anagram of 'retal'.
'retal' enclosing 'but' is 'REBUTTAL'.
(Other definitions for rebuttal that I've seen before include "A disproving or rejection of evidence" , "Refutation, contradiction" , "reply to accusation" , "resistance to attack" , "Denial" .)