Sporting bird in the main (8)
I believe the answer is:
gamecock
'the main' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'sporting bird' is the wordplay.
'sporting' becomes 'game' (I can't explain this - if you can you should believe this answer much more).
'bird' becomes 'cock' (cock is a kind of bird).
'game'+'cock'='GAMECOCK'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for gamecock that I've seen before include "Fighting bird" , "Bird trained to fight" , "featherweight fighter?" , "Footwear" .)