Brief missive (4)
I believe the answer is:
note
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">brief missive</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 note that I've seen before include "Sound, record" , "Crotchet or minim, say?" , "Make a mental or written reminder" , "Put down" , "It could be me" .)