The most common and most likely answer to this crossword clue is the 5 plus 8 letter word CIVIL ENGINEER
I've seen this crossword clue in The Daily Telegraph
C
I
V
I
L
E
N
G
I
N
E
E
R
More clues leading to the result CIVIL ENGINEER
Buddy explains!
The straight part
We know that "person such as Brunel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case person such as brunel = civil engineer.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.