'Dreck' would be a German word and means: filth, dirt, mud
'Dreak', is it possible it would be spelt 'drake'? In that case it should be another word for dragon or dragonboat (I got this from the German translation though).
I know perfectly well what "dreak" means, but if I explain it here the moderator will delete my post. Google would provide an answer much more immediately than posting here, so I leave it to Michael Place to decide if he wants to look the word up on Urban Dictionary.
I can't help suspecting, though, that the word used on Radio 3 was "dreck". In which case my original answer stands. "Dreck" means "rubbish" or "trash"; it comes from the Yiddish and may ultimately derive from the Latin "stercus", meaning "excrement".
Ivanhoe is correct - the BBC have replied to my query as follows:
"I note you were concerned to hear several times what you felt was the word ‘dreak’ on the 26 April programme.
During ‘Your Call’, Scottish listener Victor used the word ‘dreach’, which is a term used to describe gloomy, cloudy and wet weather, which most of the UK was experiencing that day. Sara does ask him to explain the meaning of the word, which he does so as ‘damp, dull and not particularly nice’.
I hope this allays your concerns, which I’d nevertheless assure you have been registered on our audience log, which is a daily report of audience feedback that’s circulated to many BBC staff, including members of the BBC Executive Board, channel controllers and other senior managers."