Fast warship (7)
I believe the answer is:
cruiser
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fast warship</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for cruiser that I've seen before include "Leisure yacht; warship" , "Warship - pleasure boat - boxing weight" , "Old warship" , "Pleasure craft" , "Relatively fast warship" .)