Sail support (4)
I believe the answer is:
mast
'sail support' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mast that I've seen before include "nuts and seeds" , "Long vertical pole" , "Long upright pole that supports sails" , "One carries the sails of a ship" , "Spar to support a sail" .)