The most common and most likely answer to this crossword clue is the 5 letter word BLOKE
I've seen this crossword clue in Financial Times
B
L
O
K
E
Buddy explains!

The straight part
We know that "an ordinary man" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an ordinary man = bloke.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 BLOKE mean?
BLOKE noun- A man, a fellow; an ordinary man, a man on the street.
- A man who behaves in a particularly laddish or overtly heterosexual manner.
- (A lower deck term for) the Captain or Executive Officer of a warship, with particular reference to discipline and punishment.
- An exemplar of a certain masculine, independent male archetype.
- An anglophone man.