The alleged victim said he met ex-Clyde and BBC Norfolk broadcaster Michael Souter after starting a casual job at the corporation in Norwich.
The witness, who cannot be named for legal reasons, told Norwich Crown Court he began doing odd jobs at Souter's home, where he claims he was abused.
Souter, 60, of Loddon, Norfolk, denies 19 sex offences, including indecent assault, indecency with a child and serious sexual offences, against seven boys aged between 11 and 16. The allegations date from between 1979 and 1999.
Souter is originally from Scotland and has worked as a producer and presenter in both commercial and BBC radio since the mid-1970s.
He had previously presented for Radio Clyde.
The witness's job, which lasted for about six months, involved helping DJs and sometimes travelling with them in a radio car with them.
He said: "I sometimes did odd jobs for Mike .
"On one occasion he offered me and a friend a beer - it was the first time I had drunk alcohol.
"I felt dizzy and the room was spinning.
"I was feeling unwell and he took me upstairs to lie down."
He told the court that when he woke up, Souter was molesting him.
The man said Souter told him 'Calm down, it's all right'."
Jurors heard the man left his job at the BBC soon after and never returned to Souter's house.
He said he did not tell anybody about the abuse.
Souter claims he has been the victim of a conspiracy. He denies he was attracted to young boys and claims none of the incidents happened.
The trial is expected to last six weeks.