First sight of enemy in some water perhaps in this? (7)
I believe the answer is:
galleon
'this?' is the definition.
The definition suggests a singular noun which matches the answer.
'first sight of enemy in some water perhaps' is the wordplay.
'first sight of' indicates taking the first letters.
'in' is an insertion indicator.
'some water perhaps' becomes 'gallon' (gallon is a unit of liquid capacity).
The first letter of 'enemy' is 'e'.
'e' put within 'gallon' is 'GALLEON'.
'in' is the link.
(Other definitions for galleon that I've seen before include "Spanish treasure ship" , "Old Spanish war-ship" , "Large old square-rigged sailing ship" , "All gone (anag.)" , "Large old sailing vessel" .)