In conclusion (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in conclusion</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for lastly that I've seen before include "In conclusion" , "In the end" , "Finally, to conclude with" .)