Swamp has a large supervisor (7)
I believe the answer is:
marshal
'supervisor' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'swamp has a large' is the wordplay.
'swamp' becomes 'marsh' (I've seen this in another clue).
'has' says to put letters next to each other.
'large' becomes 'L' (eg in clothes sizes).
'marsh'+'a'+'l'='MARSHAL'
Can you help me to learn more?
(Other definitions for marshal that I've seen before include "Sports event official" , "Arrange in order" , "US law officer" , "first officer" , "Assemble and arrange" .)