Narcotics Anonymous practise overcoming worry and disgust (8)
I believe the answer is:
nauseate
'disgust' is the definition.
(synonyms)
'narcotics anonymous practise overcoming worry' is the wordplay.
'narcotics anonymous' becomes 'NA' (abbreviation for Narcotics Anonymous).
'practise' becomes 'use' (use is a kind of practise).
'overcoming' is an insertion indicator.
'worry' becomes 'eat' (eating is a kind of worrying).
'use' enclosing 'eat' is 'useate'.
'na'+'useate'='NAUSEATE'
'and' acts as a link.
(Other definitions for nauseate that I've seen before include "Cause to feel sick" , "Sicken" , "Make to feel imminent sickness, turn stomach" , "Eaten in USA - would make you feel sick" , "Make to feel sick, revolt" .)