Young Kermit playing old tape (7)
I believe the answer is:
tadpole
'young kermit' is the definition.
(I've seen this before)
'playing old tape' is the wordplay.
'playing' is an anagram indicator.
'old'+'tape'='oldtape'
'oldtape' with letters rearranged gives 'TADPOLE'.
(Other definitions for tadpole that I've seen before include "little swimmer" , "Aquatic larva of frog or toad" , "young swimmer" , "Frog in the making" , "Aquatic larva of toads and frogs" .)