Supply son with heroin? A crime, whatever the circumstances (4,4,2,5)
I believe the answer is:
come rain or shine
'whatever the circumstances' is the definition.
(I've seen this before)
'supply son with heroin? a crime' is the wordplay.
'supply' indicates anagramming the letters ('supply' is an adverb here, so in a 'supple' way).
'with' means one lot of letters go next to another.
'son'+'heroin'+'a'+'crime'='sonheroinacrime'
'sonheroinacrime' anagrammed gives 'COME RAIN OR SHINE'.
(Other definitions for come rain or shine that I've seen before include "no matter what the circumstances may be" , "regardless of circumstances" , "Whatever the circumstances" , "Whatever the weather" .)