The most common and most likely answer to this crossword clue is the 8 letter word KNACKERS
K
N
A
C
K
E
R
S
Buddy explains!
The straight part
We know that "old hack ends up here" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old hack ends up here = knackers.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.
Crossword Answer definitions
KNACKERS noun- One who makes knickknacks, toys, etc.
- One of two or more pieces of bone or wood held loosely between the fingers, and struck together by moving the hand; a clapper.
- A harness maker.
- One who slaughters and (especially) renders worn-out livestock (especially horses) and sells their flesh, bones and hides.
- One who dismantles old ships, houses, etc. and sells their components.
- A member of the Travelling Community; a Gypsy.
- (Northern English) A person of lower social class; a chav, skanger or scobe.
- (chiefly in the plural) A testicle.
- A collier's horse.
- (UK slang) To tire out, exhaust.
- (UK slang) To reprimand.