Domestic fowl spaniel observed by English lake (8)
I believe the answer is:
cockerel
'domestic fowl' is the definition.
(I know that cockerel is a type of cock)
'spaniel observed by english lake' is the wordplay.
'spaniel' becomes 'cocker spaniel' (cocker spaniel is a kind of spaniel).
'observed by' means one lot of letters go next to another.
'english' becomes 'E' (abbreviation).
'lake' becomes 'L' (geographical abbreviation).
'cocker'+'e'+'l'='COCKEREL'
(Other definitions for cockerel that I've seen before include "Given bird" , "Young rooster" , "Farmyard bird" , "Young domestic male fowl" , "He's liable to crow" .)