Open out in self-help group revealing breathing problem (6)
I believe the answer is:
apnoea
'breathing problem' is the definition.
The definition suggests a singular noun which matches the answer.
'open out in self-help group' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'in' means one lot of letters goes inside another.
'self-help group' becomes 'aa' (Alcoholics Anonymous).
'open' anagrammed gives 'pnoe'.
'pnoe' placed inside 'aa' is 'APNOEA'.
'revealing' is the link.
Can you help me to learn more?
(Other definitions for apnoea that I've seen before include "Partial suspension of breath, in sleep say" , "Temporary suspension of breathing during sleep" , "Asphyxia" , "Transient cessation of breathing" , "choke" .)