A parting word (7)
I believe the answer is:
cheerio
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a parting word</span>' is the definition.<br/ ><span class="explanation-format__explanation">(cheerio means goodbye)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for cheerio that I've seen before include "Informal farewell" , "Ta-ta" , "A hearty farewell, begins with applause" , "See you" , "Bye-bye" .)