Immature toad or frog (7)
I believe the answer is:
tadpole
I believe this clue is a double definition.
'immature toad' is the first definition.
(I've seen this before)
'frog' is the second definition.
(I have seen 'Potential frog' mean 'tadpole' so perhaps 'frog' could also mean 'tadpole')
(Other definitions for tadpole that I've seen before include "wriggler?" , "Frog in formation" , "Pre-frog form" , "Aquatic larva of toads and frogs" , "being hatched in a puddle?" .)