The most common and most likely answer to this crossword clue is the 2 plus 4 plus 3 plus 4 letter word UP WITH THE LARK
I've seen this crossword clue in The Times
U
P
W
I
T
H
T
H
E
L
A
R
K
Buddy explains!
The straight part
We know that "Active early" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case active early = up with the lark.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.