Green’s Dictionary of Slang

(drugs) cannabis.

1992		I. Rankin Strip Jack 184: Or did you just need the time to check there was nothing to hide? A bit of blaw? That sort of thing.
2001		OnLine Dict. of Playground Sl. 🌐 blaw n. cannabis resin. e.g. ‘He smokes blaw’ Note: rhymes with ‘floor’. f. Scottish pronunciation of ‘blow’.
2006		I. Rankin Naming of the Dead ( 2007) 447: She knew plenty of officers who did a bit of blaw.