The most common and most likely answer to this crossword clue is the 5 letter word DAVID
I've seen this crossword clue in The Guardian
D
A
V
I
D
More clues leading to the result DAVID
- Daughter, passionate, celebrated nude
- Painter‘s adult representation of sex acquired by religious scholar
- Daughter’s keen on Beckham
- Fighter with five-stone advantage who beat heavyweight?
- Psalmist showing depth, devoted
- Philistine’s opponent, great French painter
- Artist beginning to draw, as keen as mustard
- One sings his praises
- Giant-killer is dead keen
- Man in Canada video
Buddy explains!

The straight part
We know that "Fighter with five-stone advantage who beat heavyweight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fighter with five-stone advantage who beat heavyweight = david.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.