The most common and most likely answer to this crossword clue is the 5 letter word STAMP
S
T
A
M
P
More clues leading to the result STAMP
- Characteristic feature of Society cheers politician
- A thrusting virtuous man Mike Pence making an impression
- Impress discontented socialist, a backbencher?
- Die for soft rugs from the east
- Print extract from Mandelstam poetry
- Character actor
- Put one’s foot down, as a matter of duty
- Character of small time politician stifling answer
- … sons stop press
- Frank put foot down
Buddy explains!

The straight part
We know that "hallmark" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hallmark = stamp.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 STAMP mean?
STAMP noun- An act of stamping the foot, paw or hoof.
- An indentation, imprint, or mark made by stamping.
- A device for stamping designs.
- A small piece of paper bearing a design on one side and adhesive on the other, used to decorate letters or craft work.
- A small piece of paper, with a design and a face value, used to prepay postage or other costs such as tax or licence fees.
- A tattoo.
- A single dose of lysergic acid diethylamide.
- A kind of heavy pestle, raised by water or steam power, for crushing ores.
- Cast; form; character; distinguishing mark or sign; evidence.
- To step quickly and heavily, once or repeatedly.
- To move (the foot or feet) quickly and heavily, once or repeatedly.
- To strike, beat, or press forcibly with the bottom of the foot, or by thrusting the foot downward.
- To mark by pressing quickly and heavily.
- To give an official marking to, generally by impressing or imprinting a design or symbol.
- To apply postage stamps to.
- To mark; to impress.