Teach a lot of young swimmers (6)
I believe the answer is:
school
This might be a double definition.
'teach a lot' is the first definition.
'school' can be an answer for 'teach' (I've seen this in another clue). I am not sure about the 'a lot' bit.
'young swimmers' is the second definition.
'school' can be an answer for 'swimmers' (group of fish). I am not sure about the 'young' bit.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for school that I've seen before include "Give instruction" , "Group of artists < in coach" , "Train (of thought?)" , "Educational tool" , "Group of pupils, fish" .)