Fight verbally
(Other definitions for argue that I've seen before include "Make a case" , "Heatedly exchange views" , "Debate or disagree" , "Contend with reasoning" , "Bandy words" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fight verbally</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for spar that I've seen before include "Crystalline mineral" , "Rafter, boom" , "Sticks" , "Box (lightly) - fight (verbally)" , "Shadow box" .)