Set phrase (5)
I believe the answer is:
idiom
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">set phrase</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for idiom that I've seen before include "Group of words in which the meaning may not be obvious" , "Linguistic peculiarity" , "Style of speaking characteristic of a specific group" , "Eg, over the moon" , "Characteristic style of a period" .)