In instalments (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in instalments</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for serial that I've seen before include "In a sequence" , "Story published in instalments" , "Story published in parts" , "Publication in instalments" , "Set of TV shows" .)
(Other definitions for episodic that I've seen before include "Serialised" , "Occurring at irregular intervals" , "Occurring irregularly - is copied accordingly" , "Discursive" , "in serial form" .)