Young swimmer whose kick is developing? (7)
I believe the answer is:
tadpole
'young swimmer' is the definition.
(young frog)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for tadpole that I've seen before include "Embryonic frog" , "Young toad" , "wriggler?" , "Immature amphibian" , "Larval form" .)