Arrangement in a straight line (9)
I believe the answer is:
alignment
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arrangement in a straight line</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 alignment that I've seen before include "Act of straightening" , "Order" , "political position" , "Collinear arrangement" , "Political side taken" .)