Ship's carrying capacity (7)
I believe the answer is:
tonnage
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ship's carrying capacity</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 tonnage that I've seen before include "Charge for carrying" , "Measure of cargo space" , "Capacity of ship" , "Weight of cargo - ship's carrying capacity" , "Ship's size or carrying capacity" .)