Winning party has significant appeal, at the end of the day (8)
I believe the answer is:
majority
'winning party' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'significant appeal at the end of the day' is the wordplay.
'significant' becomes 'major' (I've seen this before).
'appeal' becomes 'it' ('it' can mean something attractive or appealing).
'at the end of' suggests the final letters.
The last letter of 'day' is 'y'.
'major'+'it'+'y'='MAJORITY'
'has' acts as a link.
Can you help me to learn more?
(Other definitions for majority that I've seen before include "More than half the number" , "The largest group" , "Greater number or part" , "Full age" .)