Four-line stanza (8)
I believe the answer is:
quatrain
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">four-line stanza</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 quatrain that I've seen before include "Stanza or poem of four lines" , "Poetry" , "Type of verse with four lines" , "Four-line stanza" , "Four-lined verse" .)