Part of ship's mooring - need to cast off back at sea (6,4)
I believe the answer is:
engine room
'cast off back at sea' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'part of ship's mooring need' is the wordplay.
I cannot really see how this works, but
'part' could be 'in' (synonyms) and 'in' is located in the answer.
'of' could be 'o' and 'o' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for engine room that I've seen before include "hub of activity" , "basis of the Navy's power?" , "Source of naval power" , "Source of strength" .)