"Rule Britannia" composer
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rule britannia composer</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 arne that I've seen before include "Thomas --, composer of Rule, Britannia!" , "Rule Britannia composer, d. 1778" , "Rule Britannia's composer, d. 1778" , "Rule, Britannia author" .)