The most common and most likely answer to this crossword clue is the 6 letter word COOLLY
I've seen this crossword clue in The Guardian
C
O
O
L
L
Y
More clues leading to the result COOLLY
Buddy explains!

The straight part
We know that "in a less than friendly way" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in a less than friendly way = coolly.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 COOLLY mean?
COOLLY adjective- Coolish; somewhat cool in temperature
- In a cool, unpanicked or collected manner.
- With calm impudence.