Bird ranges at large in French sea (9)
I believe the answer is:
merganser
'bird' is the definition.
(merganser is a kind of bird)
'ranges at large in french sea' is the wordplay.
I cannot really understand how this works, but
an anagram of 'ranges' is 'ergans' which is located in the answer.
'sea' could be 'mer' (I have seen 'French sea ' mean 'mer' so perhaps 'sea' could also mean 'mer') and 'mer' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for merganser that I've seen before include "Diving bird" , "Diver" , "Together saw bill" , "Sawbill" , "Diving duck" .)