Partner with means to provide ladder between decks of ship (12)
I believe the answer is:
companionway
'ship' is the definition.
(thesaurus)
'partner with means to provide ladder between decks' is the wordplay.
I cannot really see how this works, but
'partner' could be 'w' and 'w' is found within the answer.
'ladder' could be 'companion' (I've seen this before) and 'companion' is present in the answer.
The remaining letters 'ay' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for companionway that I've seen before include "Ship's stair" , "Staircase on a ship" , "what gets Jack down?" , "Steps on a ship" , "Ship's ladder" .)