Ugly Duckling, eventually (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ugly duckling eventually</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 swan that I've seen before include "Mute, whooper or Bewick's bird" , "Long-necked water bird" , "The Ugly Duckling's outcome" , "Whooper, perhaps" , "Large, web-footed bird" .)