The most common and most likely answer to this crossword clue is the 8 letter word PEDIGREE
I've seen this crossword clue in The Daily Telegraph
P
E
D
I
G
R
E
E
More clues leading to the result PEDIGREE
- Pass water round mine, on descent
- Family, edgier unfortunately, after gym
- Descent from pier edge looking tricky
- Family, edgier, possibly, after training
- Family secure involvement of detective and free missing female
- Poke about in wee family tree
- Foreign father receiving taunt against European parentage
- Crack big, but not black, with deeper descent
- History of quadruped I greeted?
- Line
Buddy explains!

The straight part
We know that "line" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case line = pedigree.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 PEDIGREE mean?
PEDIGREE noun- A chart, list, or record of ancestors, to show breeding, especially distinguished breeding.
- A person's ancestral history; ancestry, lineage.
- Good breeding or ancestry.
- The history or provenance of an idea, custom etc.
- The ancestry of a domesticated animal, especially a dog or horse.
- To determine the pedigree of (an animal).
- Having a pedigree.
- Purebred.