"Sign says it all," the since-deleted post was captioned.
The sign appeared to be mocking the 2016 Democratic presidential candidate and suggesting that she herself be put in danger now.
Clinton was serving secretary of state during the 2012 attack on the American consulate in Benghazi, Libya. US ambassador to Libya Christopher Stevens and three other Americans were killed in the assault. Clinton has faced significant criticism from Republicans who accused her of being personally responsible for security lapses in Benghazi.
A Clinton spokesman did not immediately return a CNN request for comment Monday night. Brat's office also didn't immediately return a request for comment.
Brat told a Richmond television station, WWBT NBC 12
, that he did not put the picture up himself and noted that he has some new staffers working for him, adding, "if this can be interpreted in any way as negative in that way -- I apologize for that."
Still, Brat rejected the idea that the sign in any way suggested Clinton be put in danger.
"No, that's -- that's laughable, right?" he told the Richmond-based news station.
In a later post to his Instagram account, Brat said he thought the sign has been misinterpreted.
"Dear Instagram friends, an earlier pic today was being misinterpreted so it has been removed," the post read.
Asked by the news station if the sign bothered him at all, Brat said, "No, I thought the guy was just getting at the Benghazi injustice that everybody knows is a tragedy -- it had to do with all these tapes and stuff," according to the station's write-up of the interview.
The congressman did not offer a clear explanation as to why the sign said Clinton should be ambassador to Libya.