Happy with adult breaking sullen daughter's unfair rule (6,8)

I believe the answer is:

double standard

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'unfair rule' is the definition.

'happy with adult breaking sullen daughter's' is the wordplay.
'happy' becomes 'blest' (archaic form of blessed).
'with adult' becomes 'anda' (I am not sure about this - if you are sure you should believe this answer much more).
'breaking' is an insertion indicator.
'sullen' becomes 'dour' (synonyms).
'daughter' becomes 'd'.
'blest'+'anda'='blestanda'
'blestanda' put into 'dour' is 'doublestandar'.
'doublestandar'+'d'='DOUBLE STANDARD'

Can you help me to learn more?

(Other definitions for double standard that I've seen before include "inconsistent principle?" , "Rule applied unfairly" .)

I've seen this clue in The Telegraph.

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