Four seasons (4)
I believe the answer is:
year
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">four seasons</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for year that I've seen before include "eg 2004" , "See 33 Across" , "One orbit round the sun" , "One intake of undergrads" , "Many students" .)