Deckhands finally got out of sweeping vessel (3)
I believe the answer is:
vat
'sweeping vessel' is the definition.
'vat' can be an answer for 'vessel' (vat is a kind of vessel). I am not certain of the 'sweeping' bit.
'deckhands finally got' is the wordplay.
'deckhands' becomes 'va' (I am not sure about this - if you are sure you should believe this answer much more).
'finally' says to take the final letters.
The final letter of 'got' is 't'.
'va'+'t'='VAT'
'out of' is the link.
Can you help me to learn more?
(Other definitions for vat that I've seen before include "A tax on a large container?" , "Large tank; purchase tax" , "possible source of liquid" , "Large container for liquid" , "Large tank for liquids, or kind of tax" .)