The Burundi-born England Under-20 international scored against Walsall on Tuesday to underline a productive second-half display.
"Berahino is someone I brought on at half-time on Tuesday because we wanted someone who could run behind their defence," Clarke told the Birmingham Mail.
"He can do that. He's done well this pre-season. He hasn't played many minutes on the pitch but I've seen him work in training, be in and around the squad and I'm pleased with him.
"He's done very well and did everything I asked of him against Walsall, also scoring a good goal in the process."