Towboat (3)
I believe the answer is:
tug
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">towboat</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tug that I've seen before include "Pull like small boat" , "Pull suddenly; boat" , "Pull at the towing vessel" , "Small boat for towing others" , "Boat to pull larger one" .)