The most common and most likely answer to this crossword clue is the 15 letter word PITHECANTHROPUS
I've seen this crossword clue in The Times
P
I
T
H
E
C
A
N
T
H
R
O
P
U
S
More clues leading to the result PITHECANTHROPUS
- After depression, the ranch arranged new work for old man
- Ancestor of mine: the fellow isn't able to get personnel work
- Unable to work with personnel east of mine? He’s an old man
- Old man in mine, he is unable to regularly take hard work
- Thin chap, posture bent, forerunner of Man?
- Apelike man right inside quarry-he isn't able to jump us
- Original top hunter chap is … me?
- Up north, pastiche irritated primitive sort
Buddy explains!
The straight part
We know that "old man" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old man = pithecanthropus.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.