Green’s Dictionary of Slang

(US black) a (recording) studio.

2011		Urban Dict. 5 Sept. 🌐 stu [...] A room where artists work, write, record songs and get high.
2017		Young M.A. ‘Walk’ 🎵 I was working at the house, in the stu’ / Sleepin’ on the couch.
2021		Central Cee ‘Sex Money Drugs’ 🎵 Told her ‘I’m in the stu all night, hold tight, I’ll reply in the morning’.