Holiday at sea (6)
I believe the answer is:
cruise
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">holiday at sea</span>' is the definition.<br/ ><span class="explanation-format__explanation">(holiday on a ship)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for cruise that I've seen before include "Holiday afloat - Kidman's ex" , "Pleasure ocean voyage" , "Ship holiday" , "Ocean trip taken for pleasure" , "Voyage for holiday makers" .)