Vessel without Spanish gold is getting fruit (7)
I believe the answer is:
sorosis
'fruit' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I don't see?
'vessel without spanish gold is' is the wordplay.
'vessel' becomes 'SS' (prefix in ship names eg SS Great Britain).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'spanish gold' becomes 'oro' (I've seen this in another clue).
'ss' going around 'oro' is 'soros'.
'soros'+'is'='SOROSIS'
'getting' acts as a link.
Can you help me to learn more?
(Another definition for sorosis that I've seen is " fruit like the pineapple".)