Aft (6)
I believe the answer is:
astern
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">aft</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 astern that I've seen before include "(In relation to ship) behind" , "Towards rear of a vessel" , "at the vessel's rear" , "Ran set (anag.)" , "State of S central US" .)