Waterway used for wonderful marriage with tin, aluminium (5,5,5)
I believe the answer is:
grand union canal
'waterway used' is the definition.
I can't tell whether this definition defines the answer.
'wonderful marriage with tin aluminium' is the wordplay.
'wonderful' becomes 'grand' (I've seen this in another clue).
'marriage with' becomes 'union' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tin' becomes 'can' (synonyms).
'aluminium' becomes 'al' (chemical symbol).
'grand'+'union'+'can'+'al'='GRAND UNION CANAL'
'for' is the link.
Can you help me to learn more?
(Other definitions for grand union canal that I've seen before include "watercourse" , "Way with water" .)