The most common and most likely answer to this crossword clue is the 8 plus 4 letter word MARITIME ALPS
I've seen this crossword clue in Financial Times
M
A
R
I
T
I
M
E
A
L
P
S
More clues leading to the result MARITIME ALPS
Buddy explains!
The straight part
We know that "group having its ups and downs in Europe" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case group having its ups and downs in europe = maritime alps.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.