The most common and most likely answer to this crossword clue is the 7 letter word RIPOSTE
I've seen this crossword clue in The Sunday Telegraph
R
I
P
O
S
T
E
More clues leading to the result RIPOSTE
- Old saint put in mature, clever reply
- Ceremony embracing sailor’s swift comeback
- Sally ready to embrace East German
- Clever reply from Republican that is shown round office
- No way hiding, ready for quick thrust
- Sally, I notice, runs to the front
- Reply regarding limiting one comment on forum
- Poster I upset making clever reply
- Finally after I contributed to forum, maybe daughter deleted reply
- Ceremony welcoming pilot officer's return
Buddy explains!

The straight part
We know that "Quickly reply" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case quickly reply = riposte.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 RIPOSTE mean?
RIPOSTE noun- A thrust given in return after parrying an attack.
- A counter-attack in any combat or any sport
- A quick and usually witty response to a taunt, a retort
- An answer or reply, rapidly uttered, in response to a question or problem
- To attempt to hit an opponent after parrying an attack.
- To respond quickly; particularly if the response is humorous.