At the back (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">at the back</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 astern that I've seen before include "Ran set (anag.)" , "State of S central US" , "Behind at sea" , "Towards the rear of boat" , "back for sailors" .)
(Other definitions for behind that I've seen before include "Not up to date" , "support" , "Hidden by; bottom" , "Responsible for" , "At the back of" .)