They are not yet at the croaking stage (8)
I believe the answer is:
tadpoles
'they' is the definition.
Both the answer and definition are plural nouns.
Maybe they are linked in a way I don't understand?
'are not yet at the croaking stage' is the wordplay.
I cannot really see how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is found in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tadpoles that I've seen before include "Larval frogs" , "Stop deal (anag.)" , "Immature frogs" , "Young frogs" , "Baby frogs" .)