The final round (4,3)
I believe the answer is:
last lap
'the' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'final round' is the wordplay.
'final' becomes 'last' (synonyms).
'round' becomes 'lap' (as in a round or lap of a park).
'last'+'lap'='LAST LAP'
Can you help me to learn more?
(Other definitions for last lap that I've seen before include "Final stretch or round of track" , "Final circuit of track in race" , "Final part of race" .)