The most common and most likely answer to this crossword clue is the 7 letter word NIBBLER
N
I
B
B
L
E
R
Buddy explains!

The straight part
We know that "he’s biting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case he’s biting = nibbler.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 NIBBLER mean?
NIBBLER noun- Someone who nibbles.
- A tool for cutting sheet metal.
- A fish of the sea chub subfamily Girellinae.
- A kind of program for copying protected floppy disks.