Bird with a big bill for fish (7)
I believe the answer is:
pelican
'bird' is the definition.
(pelican is a kind of bird)
'a big bill for fish' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is found within the answer.
This explanation may well be incorrect...
'with' acts as a link.
Can you help me to learn more?
(Other definitions for pelican that I've seen before include "Bird with enormous bill" , "Water bird with throat pouch for fish" , "Aquatic, billed bird" , "Tropical bird" , "Does its beak hold more that its belly can?" .)