Adverb describing generally wreckless behaviour, i.e. someone who does something bad/anti-social in public without giving a fuck about being noticed by police, disapproving bystanders, etc.
He sparked up the lemon rago, right under old bill's nose!
Term originating in London, referring to high-grade skunk (hydroponically-cultivated marijuana). Describes hydro that is 'above average' in terms of potency/quality. Widely used term in UK Grime music.
'This shit is the lemon!'
or...
'My man's got the lemon!'.