The most common and most likely answer to this crossword clue is the 4 plus 7 letter word HOME STRETCH
I've seen this crossword clue in The Daily Telegraph
H
O
M
E
S
T
R
E
T
C
H
More clues leading to the result HOME STRETCH
Buddy explains!
The straight part
We know that "Final stage" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case final stage = home stretch.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.