Single-masted vessel (6)
(Other definitions for cutter that I've seen before include "Ship's boat" , "Fast boat; blade" , "A scissors, say, or a small ship" , "Small sailing ship or a knife" , "Slicing tool of fast sailing ship" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">single-masted vessel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sloop that I've seen before include "Single-masted sailing vessel" , "Type of sailing boat" , "Sailing vessel with one mast" , "one going to sea" , "One-masted sailing boat" .)