Fantastic innings at an end (8)
I believe the answer is:
knockout
'an end' is the definition.
(I have seen 'End of bout' mean 'knockout' so perhaps 'end' could also mean 'knockout')
'fantastic innings' is the wordplay.
I cannot quite understand how this works, but
'innings' could be 'knock' (I've seen this in other clues) and 'knock' is present in the answer.
The remaining letters 'out' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'at' is the link.
Can you help me to learn more?
(Other definitions for knockout that I've seen before include "Act of rendering unconscious" , "decisive result" , "Decisive punch" , "Blow that renders the opponent unconscious" , "Render senseless" .)