The most common and most likely answer to this crossword clue is the 6 letter word BOATER
I've seen this crossword clue in The Guardian
B
O
A
T
E
R
Buddy explains!
The straight part
We know that "chap having a row, say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case chap having a row, say = boater.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 BOATER mean?
BOATER noun- Someone who travels by boat.
- One who works on a boat, especially as captain.
- A straw hat, very stiff, with a flat brim and crown.