The most common and most likely answer to this crossword clue is the 7 letter word ECOLOGY
I've seen this crossword clue in The Daily Telegraph
E
C
O
L
O
G
Y
Buddy explains!

The straight part
We know that "environmental matters" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case environmental matters = ecology.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 ECOLOGY mean?
ECOLOGY noun- The branch of biology dealing with the relationships of organisms with their environment and with each other.