Sounds weak, but will probably hold water (4)
I believe the answer is:
pail
'will probably hold water' is the definition.
I can't judge whether this defines the answer.
'sounds weak' is the wordplay.
'sounds' shows a homophone (sound like).
'weak' becomes 'pale' (similar in meaning).
'pale' sounds like 'PAIL'.
'but' is the link.
Can you help me to learn more?
(Other definitions for pail that I've seen before include "Vessel for carrying liquids" , "Kind of bucket - ask Jack and Jill" , "Container; sounds like dim" , "water-carrier" , "Milkmaid's bucket?" .)