Vessel fitted with a royal navy hooter (4,3)

I believe the answer is:
barn owl
'hooter' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'vessel fitted with a royal navy' is the wordplay.
'vessel' becomes 'bowl' (bowl is a kind of vessel).
'fitted with' indicates putting letters inside.
'royal navy' becomes 'RN' (abbreviation for Royal Navy).
'a'+'rn'='arn'
'bowl' placed around 'arn' is 'BARN-OWL'.
Can you help me to learn more?
(Other definitions for barn owl that I've seen before include "Endangered night bird" , "Nocturnal raptor" , "Mottled buff and white night bird" , "Nocturnal bird native to Britain" , "Night-flying raptor" .)
