Little European pond-dweller (7)
I believe the answer is:
tadpole
'pond-dweller' is the definition.
(a tadpole might live in a pond)
'little european' is the wordplay.
'little' becomes 'tad' (both can mean a small amount).
'european' becomes 'Pole' (someone from Poland).
'tad'+'pole'='TADPOLE'
(Other definitions for tadpole that I've seen before include "wriggler?" , "Aquatic larva of frog or toad" , "Legless creature" , "A frog-to-be" , "Larval form" .)