Ship's primary means of propulsion using blades? (5)
I believe the answer is:
screw
'ship's' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for screw that I've seen before include "Fastener with a tapered threaded shank" , "Fixer; twist of paper" , "Old horse" , "Bring pressure to bear" , "Threaded pin" .)