Secret language (4)
I believe the answer is:
code
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">secret language</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for code that I've seen before include "Computer language, say" , "See 21 Across" , "System of words arrangement for secrecy" , "Established standards" , "Program instruction" .)