Suffix for a superlative (3)
I believe the answer is:
est
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">suffix for a superlative</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 est that I've seen before include "self-improvement programme" , "Suffix showing superlative" , "Time Americans adopted" , "psychological programme" .)