The most common and most likely answer to this crossword clue is the 8 letter word RIPOSTED
I've seen this crossword clue in The Sunday Telegraph
R
I
P
O
S
T
E
D
More clues leading to the result RIPOSTED
Buddy explains!

The straight part
We know that "Quickly responded" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case quickly responded = riposted.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 RIPOSTED mean?
RIPOSTED verb- To attempt to hit an opponent after parrying an attack.
- To respond quickly; particularly if the response is humorous.