The most common and most likely answer to this crossword clue is the 13 letter word OVERABUNDANCE
O
V
E
R
A
B
U
N
D
A
N
C
E
More clues leading to the result OVERABUNDANCE
Buddy explains!
The straight part
We know that "excess" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case excess = overabundance.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.
Crossword Answer definitions
OVERABUNDANCE noun- An excess of what is needed or is appropriate.