Academy for swimmers? (6)
I believe the answer is:
school
I believe this is a double definition.
'academy' is the first definition.
(I've seen this in another clue)
'swimmers?' is the second definition.
(group of fish)
'for' is the link.
(Other definitions for school that I've seen before include "Institute of education" , "Large group of fish" , "Educational facility" , "Give instruction" , "Group of pupils, fish" .)