Crow's-nest support (4)
I believe the answer is:
mast
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crow's-nest support</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 mast that I've seen before include "Pole aboard; fruit for pigs" , "nuts and seeds" , "it rises on board a ship" , "Television transmitter" , "Vertical spar for supporting sails etc" .)