One eats a lot of fish, large one in some pie filling (7)

I believe the answer is:
pelican
'one eats a lot' is the definition.
I can't tell whether this defines the answer.
'fish large one in some pie filling' is the wordplay.
'fish' becomes 'pecan' (I can't justify this - if you can you should believe this answer much more).
'large' becomes 'L' (eg in clothes sizes).
'one in' indicates putting letters inside.
'some' indicates the central letters.
'filling' indicates putting letters inside.
The centre of 'pie' is 'i'.
'pecan' enclosing 'l' is 'pelcan'.
'pelcan' going around 'i' is 'PELICAN'.
'of' is the link.
Can you help me to learn more?
(Other definitions for pelican that I've seen before include "Large bird with pouch in bill for storing fish" , "one with huge bill" , "Aquatic, billed bird" , "Large-billed waterbird" , "The large bird is in place" .)
