The most common and most likely answer to this crossword clue is the 2 plus 3 plus 2 plus 3 letter word TO CAP IT ALL
I've seen this crossword clue in The Times
T
O
C
A
P
I
T
A
L
L
More clues leading to the result TO CAP IT ALL
- Finally up late, not having had a meal
- The final insult? Charge cut by 25 per cent eats funds
- On top of everything else, item for auction rejected across London, for instance
- What’s more, many back taking on Brussels, for example
- Charge, briefly, involves money invested on top of everything else
- Retired group touring Paris, perhaps as a climax
Buddy explains!

The straight part
We know that "Finally" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case finally = to cap it all.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.