The most common and most likely answer to this crossword clue is the 7 letter word TROOPER
I've seen this crossword clue in The Times
T
R
O
O
P
E
R
More clues leading to the result TROOPER
- Bring information back about old soldier
- Soldier drunk, other ranks caught up
- Soldier’s rejected report about start of offensive
- Soldier brought up in care, poor thing
- One supposedly swearing there's nothing in false report
- Soldier’s account holding nothing back
- Case dispensed with, grog drunk by inebriate in private
- Foul-mouthed one maybe bringing up rumour with nothing in it
- Recollection of news about old soldier
- One expected to swear he’s a soldier
Buddy explains!

The straight part
We know that "One supposedly swearing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one supposedly swearing = trooper.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 TROOPER mean?
TROOPER noun- A soldier of private rank in cavalry or armour.
- A cavalry horse; charger.
- A soldier.
- A troopship.
- A state trooper.
- A mounted policeman.
- One who endures adversity or hardship with an attitude of stoicism and persistence.
- To work as a trooper.
- To work steadily at an unpleasant job without complaint.