Shearwater, say, found by domestic animal on lake (6)
I believe the answer is:
petrel
'shearwater say' is the definition.
(shearwater is a kind of petrel)
'by domestic animal on lake' is the wordplay.
'by' says to put letters next to each other.
'domestic animal' becomes 'pet' (animal kept in the home).
'on' becomes 're' (regarding).
'lake' becomes 'L' (geographical abbreviation).
'pet' put next to 're' is 'petre'.
'petre'+'l'='PETREL'
'found' is the link.
(Other definitions for petrel that I've seen before include "Bird of storms at sea" , "Seabird (that may be stormy)" , "The sea-bird known as stormy" , "Seabird sounds like fuel" , "Storm bird" .)