Decline daughter -- that is a method (3,4)

I believe the answer is:

die away

'decline' is the definition.
(thesaurus)

'daughter that is a method' is the wordplay.
'daughter' becomes 'd'.
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'method' becomes 'way' (I've seen this before).
'd'+'ie'+'a'+'way'='DIE-AWAY'

(Another definition for die away that I've seen is " slowly fade out".)

I've seen this clue in The Telegraph.

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