The most common and most likely answer to this crossword clue is the 7 letter word ATTUNES
I've seen this crossword clue in Independent
A
T
T
U
N
E
S
More clues leading to the result ATTUNES
Buddy explains!

The straight part
We know that "Becomes acclimatised to" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case becomes acclimatised to = attunes.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 ATTUNES mean?
ATTUNES verb- To bring into musical accord.
- To tune (an instrument).
- To bring into harmony or accord.