The most common and most likely answer to this crossword clue is the 7 letter word RUSSELL
R
U
S
S
E
L
L
More clues leading to the result RUSSELL
- Start to resent hype possibly surrounding American philosopher
- Philosopher to take stock, it’s reported
- After scheme falls short get rid of mathematician
- Game’s deception
- Brand market drops 25% after collapse of USSR
- 16 sound of sound made by Jack
- Extremists will desert EU, old chap
- Square fellow
- Sport is ultimately a disappointment for a philosopher
- Brief plan to promote actress
Buddy explains!

The straight part
We know that "chap" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case chap = russell.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.