Seasonal wind (7)
I believe the answer is:
monsoon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">seasonal wind</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 monsoon that I've seen before include "Seasonal wind (south-west or north-east) of southern Asia" , "Rain-bringing weather feature" , "Asian wind; rainy season" , "Seasonal wind or rainy season in S Asia" , "Rainy season in southern Asia" .)