Reason for doing very little crack and heroin (5)

I believe the answer is:
sloth
'reason' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'doing very little crack and heroin' is the wordplay.
'doing very' becomes 'sot' (I can't explain this - if you can you should give a lot more credence to this answer).
'little' becomes 'l' (abbreviation).
'crack' is an insertion indicator (inserted letters go into a gap or crack).
'and' says to put letters next to each other.
'heroin' becomes 'H' (H is a slang term for heroin).
'sot' going around 'l' is 'slot'.
'slot'+'h'='SLOTH'
'for' is the link.
Can you help me to learn more?
(Other definitions for sloth that I've seen before include "Lethargy" , "A deadly sin, being lazy" , "Aversion to industry" , "Arboreal creature" , "Idleness" .)
