Pothead in rehab - they dropped pill in boredom (6)
I believe the answer is:
apathy
'boredom' is the definition.
(thesaurus)
'pothead in rehab they dropped pill' is the wordplay.
'pothead' becomes 'p' (head letter of 'pot').
'in' is an insertion indicator.
'rehab' becomes 'aa' (I am not sure about this - if you are sure you should believe this answer much more).
'dropped' suggests deleting specific letters.
'pill' becomes 'e' (ecstasy).
'they' with 'e' taken away is 'thy'.
'p' inserted within 'aa' is 'apa'.
'apa'+'thy'='APATHY'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for apathy that I've seen before include "Indifference, emotionlessness" , "Unconcern" , "Lack of excitement" , "Lack of interest or concern" , "Complete lack of interest, indifference" .)