Aid to memory (8)
I believe the answer is:
mnemonic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">aid to memory</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 mnemonic that I've seen before include "That which helps memory, a rhyme say" , "Trigger for the memory" , "Letters aiding memory" , "Something by which to remember" , "It aids recall" .)