River scene of historic battle in navy service (4)
I believe the answer is:
yser
'river scene of historic battle' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'navy service' is the wordplay.
'YSER' is hidden in amongst the letters.
But, I'm uncertain how this is indicated.
'in' is the link.
Can you help me to learn more?
(Other definitions for yser that I've seen before include "European flower" , "Glum" , "Belgian river associated with Flanders battleground" , "River -- battle scene in First World War" , "European river" .)