Albatross? Eagle? Yes and no! (6)
I believe the answer is:
birdie
'no' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'albatross? eagle? yes' is the wordplay.
'albatross?' becomes 'bird' (albatross is a kind of bird).
'eagle? yes' becomes 'ie' (I can't explain this - if you can you should give a lot more credence to this answer).
'bird'+'ie'='BIRDIE'
'and' acts as a link.
(Other definitions for birdie that I've seen before include "One watched" , "In golf, a score of one under par for the hole" , "One under in 20 across" , "One under par - watch it!" , "low score" .)