The phrase "a reply which" is correct and usable in written English.
It can be used when introducing a specific response or answer that is being referred to in a discussion or text.
Example: "I appreciate a reply which addresses all my concerns regarding the project."
Alternatives: "a response that" or "an answer which".
"Possibly," I said, a reply which makes Chisora grin broadly.
We received a reply, which was in effect a no-reply.
"I don't know," says Spitzer, a reply which would be hilarious if it wasn't so disgraceful.
E-Max will let users record a reply, which is sent as an audio file in an e-mail attachment.
Some interpreted it to mean that every email deserved a reply, which only shackled them more firmly to their inboxes.
I emailed Amazon early on Sunday and finally received a reply (which some in the media have interpreted as an apology): Thank you for contacting Amazon.com.
In 1982, Smith wrote a letter to the newly appointed CPSU General Secretary Yuri Andropov, and received a personal reply which included a personal invitation to visit the Soviet Union, which she accepted.
Ramus, attacked by a colleague, took only three days to produce a witty reply, which was printed a few days later with Talon's name on the title-page, though the latter had barely seen the manuscript (Nancelius, pp. 219 221).
He received a lengthy reply, which wound up, "I am surprised that a man of your training and mental capacities should place such reliance on the word of our salesman.
See Schimmack & Oishi (2005) for a critical reply, which argues that chronically accessible information is a much better predictor of life satisfaction responses than temporarily accessible information, such as how many dates one went on last week.
A guest at the dinner had asked the mayor for his feelings about the two candidates, prompting a lengthy reply, which was overheard by other guests.
