Definition of "phet"

My uncle is a big "phet" dealer and partners with my aunt. My dad is an alcoholic smackhead with nowhere to live apart from the pub and his fishing boat.

2001, Pretext, page 105

Barry knew what this was about. Barry said to him, 'Chris. All right? No worries, Chris. I've told you. You'll get your money. I just need some time to get sorted.' A few years ago Barry was meant to deliver some phet for Little Chris to a flat on the Meadows estate. […] when he came back outside, the car had gone. So had the drugs.

2015, SPCK, Bare Freedom, SPCK