In times gone by (4)
I believe the answer is:
once
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in times gone by</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 once that I've seen before include "A single time" , "One-time musical film and song" , "At some former time" , "In days past" , "Long ago" .)