Pin for propeller (5)
I believe the answer is:
screw
I believe this is a double definition.
'pin' is the first definition.
(thesaurus)
'propeller' is the second definition.
(screw is a kind of propeller)
'for' acts as a link.
(Other definitions for screw that I've seen before include "Prison officer (slang)" , "Hack" , "Helical thread" , "shaft" , "Apply backspin (snooker)" .)