Flocks of birds -- where you'll see beaks (7)
I believe the answer is:
schools
I believe this clue is a double definition.
'flocks of birds' is the first definition.
(school can mean a flock of birds)
'where you'll see beaks' is the second definition.
(beak can informally mean a school teacher)
(Other definitions for schools that I've seen before include "dolphins in groups, for example" , "Institutions of learning" , "Colleges" , "Coaches, trains" , "Places of instruction" .)