The most common and most likely answer to this crossword clue is the 7 letter word RISKIER
I've seen this crossword clue in The Daily Telegraph
R
I
S
K
I
E
R
More clues leading to the result RISKIER
- Upset Irish winter sportsman? That’s more dangerous
- Standing up Irish athlete is more dangerous
- Alpine enthusiast after run, one more perilous
- Following run on icy surface winter sports enthusiast is more reckless
- Runs one downhiller maybe finds more dangerous
- I run up, one likely to slide — it’s not so safe
- Starting round one, sportsman going downhill is less certain of success
- More dangerous for one gliding down mountain after odd rain
- Runs one sportsman finds more dangerous
- Rhode Island winter athlete is not so safe
Buddy explains!

The straight part
We know that "not so safe" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not so safe = riskier.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.
What does RISKIER mean?
RISKIER adjective- Dangerous, involving risks.