At no cost (6)
I believe the answer is:
gratis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">at no cost</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for gratis that I've seen before include "Free, costs nothing" , "Free (Latin)" , "Free of charge" , "Free, at no cost" , "not charged" .)