Enclosed rhyme scheme (4)
I believe the answer is:
abba
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">enclosed rhyme scheme</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 abba that I've seen before include "Old group" , "rhymes in Petrarchan sonnet" , "6 24 113 [SCAN-DIN-AVIAN] band" , "Eurovision winners" , "Pater's" .)