Sinbad and Noah quietly conspired to jump overboard (7,4)
I believe the answer is:
abandon ship
'conspired to jump overboard' is the definition.
I know nothing about this answer so I can't judge whether this works.
'sinbad and noah quietly' is the wordplay.
I cannot quite see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
'quietly' could be 'sh' (both are used to tell someone to be quiet) and 'sh' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abandon ship that I've seen before include "Leave a sinking vessel" , "Go overboard" , "get into lifeboats" .)