The most common and most likely answer to this crossword clue is the 6 letter word REAPER
I've seen this crossword clue in The Times
R
E
A
P
E
R
More clues leading to the result REAPER
- Harvest worker extremely prone to break back
- Person taking off after touching farm machinery
- Back, having secured extremely portable farm machine
- Part of area perfect for harvester
- Arse takes exercise – death personified!
- One using a scythe, back- breaking exercise?
- Harvester in back-breaking exercise?
- Pie with no filling consumed by stern, grim figure?
- One gathers that you don’t want to meet if it’s grim
- Farm worker needing exercises with restrictive back
Buddy explains!

The straight part
We know that "farm machinery" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case farm machinery = reaper.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 REAPER mean?
REAPER noun- One who reaps.
- A machine used to harvest crops.
- (often with initial capital) Short for Grim Reaper.