Small seal and young aquatic bird reported (6)
I believe the answer is:
signet
'small seal' is the definition.
(type of official seal)
'young aquatic bird reported' is the wordplay.
'young aquatic bird' becomes 'cygnet' (I've seen this before).
'reported' indicates a 'sounds like' (homophone) clue.
'cygnet' is a homophone of 'SIGNET'.
'and' is the link.
(Other definitions for signet that I've seen before include "Official seal" , "Small seal, on ring perhaps" , "Kind of ring with seal" , "Ingest in ring" , "'Seal, on a ring say (6)'" .)