Beastly cross by the end of the story! (4)
I believe the answer is:
oryx
'end of the story' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'beastly cross by' is the wordplay.
'beastly cross' becomes 'ory' (I can't explain this - if you can you should believe this answer much more).
'by' becomes 'x' (r by 4 is r x 4).
'ory'+'x'='ORYX'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for oryx that I've seen before include "African native" , "Long-horned African antelope" , "horny beast" , "African long-horned grazer" , "creature" .)