One of those holding up the boat (5)
I believe the answer is:
davit
'boat' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for davit that I've seen before include "device for lowering boat" , "Lifeboat crane" , "nautical equipment" , "Crane-like device for suspending or lowering ship's boats" .)