The most common and most likely answer to this crossword clue is the 6 letter word GRAHAM
G
R
A
H
A
M
Buddy explains!

The straight part
We know that "This fellow" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case this fellow = graham.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 GRAHAM mean?
GRAHAM noun- Flour made by grinding wheat berries including the bran.
- A graham cracker.