Unifying idea (5)
I believe the answer is:
theme
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unifying idea</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for theme that I've seen before include "Subject (of talk, text, etc)" , "Topic, leitmotif" , "idea of the work" , "Thread, melody" , "[(type of) PARK]" .)