Lead pot broken by the larva (7)
I believe the answer is:
tadpole
'the larva' is the definition.
(tadpole is a kind of larva)
'lead pot broken' is the wordplay.
'broken' is an anagram indicator.
'lead'+'pot'='leadpot'
'leadpot' anagrammed gives 'TADPOLE'.
'by' is the link.
(Other definitions for tadpole that I've seen before include "frog may spring from" , "Young frog" , "Frog in the making" , "wriggler?" , "Young toad" .)