Aren't ropes aboard ship very good quality? (11)
I believe the answer is:
saintliness
'good quality?' is the definition.
'saintliness' can be an answer for 'quality?' (saintliness is a kind of quality). I'm unsure of the 'good' bit.
'aren't ropes aboard ship' is the wordplay.
'aren't' becomes 'ain't' (non-standard version of 'isn't' or 'aren't').
'ropes' becomes 'lines' (I am not sure about this - if you are sure you should believe this answer much more).
'aboard' is an insertion indicator.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'aint'+'lines'='aintlines'
'aintlines' inserted inside 'ss' is 'SAINTLINESS'.
'very' is the link.
Can you help me to learn more?
(Other definitions for saintliness that I've seen before include "being very good" , "Least in sins (anag)" .)