The most common and most likely answer to this crossword clue is the 3 letter word CAN
I've seen this crossword clue in The Times
C
A
N
More clues leading to the result CAN
- Is able to seal in tin
- Stick, almost all, in tin
- Stop work on prison
- Cryptic clue maybe not about verse in pop song
- Preserve in aspic a nut
- Is able to shorten stick
- Confident, furthermore, entering business
- Is able to let go in the US
- Somewhat frantic and oddly positive in attitude
- Preserve word Americans, Canadians, and Mexicans have in common
Buddy explains!

The straight part
We know that "Confident" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case confident = can.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 CAN mean?
CAN verb- (auxiliary verb, defective) To know how to; to be able to.
- (modal auxiliary verb, defective) May; to be permitted or enabled to.
- (modal auxiliary verb, defective) To have the potential to; be possible.
- (auxiliary verb, defective) Used with verbs of perception.
- To know.
- A more or less cylindrical vessel for liquids, usually of steel or aluminium, but sometimes of plastic, and with a carrying handle over the top.
- A container used to carry and dispense water for plants (a watering can).
- A tin-plate canister, often cylindrical, for preserved foods such as fruit, meat, or fish.
- A chamber pot, now a toilet or lavatory.
- Buttocks.
- Jail or prison.
- (in the plural) Headphones.
- A drinking cup.
- A cube-shaped buoy or marker used to denote a port-side lateral mark
- A chimney pot.
- (in the plural) an E-meter used in Scientology auditing.
- To seal in a can.
- To preserve by heating and sealing in a jar or can.
- To discard, scrap or terminate (an idea, project, etc.).
- To shut up.
- To fire or dismiss an employee.
- To hole the ball.