Military vessel (7)
(Other definitions for battleship that I've seen before include "craft for action" , "Eisenstein film about 1905 revolt" , "Large navy vessel" , "Vessel of war" , "naval craft" .)
(Other definitions for warship that I've seen before include "Eg, destroyer, cruiser" , "Navy asset" , "frigate perhaps" , "Naval asset" , "It's armed at sea" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">military vessel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for gunboat that I've seen before include "Small military ship" , "Naval symbol of aggression" , "Military vessel" , "Not a bug (anag)" , "Small armed vessel" .)