Little rod used for pond-life? (7)
I believe the answer is:
tadpole
'for pond-life?' is the definition.
(tadpoles live in ponds)
'little rod' is the wordplay.
'little' becomes 'tad' (both can mean a small amount).
'rod' becomes 'pole' (pole is a kind of rod).
'tad'+'pole'='TADPOLE'
'used' is the link.
(Other definitions for tadpole that I've seen before include "youngster" , "Larval form" , "Future frog maybe" , "developed from spawn" , "Frog in the making" .)