Of purely theoretical interest (8)
I believe the answer is:
academic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">of purely theoretical interest</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 academic that I've seen before include "Theoretical or scholarly - often not practical" , "Of theoretical interest, no practical application" , "Not expected to produce any practical result" , "Irrelevant; teacher" , "Well-read" .)