The most common and most likely answer to this crossword clue is the 7 plus 2 plus 6 letter word REQUIRE AN ANSWER
I've seen this crossword clue in Financial Times
R
E
Q
U
I
R
E
A
N
A
N
S
W
E
R
Buddy explains!
The straight part
We know that "Want a reply" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case want a reply = require an answer.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.