Big bird, say, that has upset old man, getting in way (8)
I believe the answer is:
megapode
'big bird say' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'upset old man getting in way' is the wordplay.
'upset' says the letters should be written in reverse.
'old man getting' becomes 'page' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'way' becomes 'mode' (synonyms).
'page' reversed gives 'egap'.
'egap' going within 'mode' is 'MEGAPODE'.
'that has' is the link.
Can you help me to learn more?
(Other definitions for megapode that I've seen before include "Aussie bird" , "Mound Builder" , "Australian mallee fowl" .)