Ship from east in fluid measure (7)
I believe the answer is:
galleon
'ship' is the definition.
(type of ship)
'from east in fluid measure' is the wordplay.
'from east' is a reversal indicator.
'in fluid' becomes 'noel' (I can't justify this - if you can you should believe this answer much more).
'measure' becomes 'lag' (lag is a kind of measure).
'noel'+'lag'='noellag'
'noellag' back-to-front is 'GALLEON'.
Can you help me to learn more?
(Other definitions for galleon that I've seen before include "One might sink" , "Old Spanish war-ship" , "All gone (anag.)" , "Ship of the line" , "Trader" .)