Father adopting an excellent cure for everything (7)
I believe the answer is:
panacea
'cure for everything' is the definition.
(I've seen this before)
'father adopting an excellent' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'adopting' means one lot of letters goes inside another (inserted letters are taken on or adopted).
'excellent' becomes 'ace' (ace can informally mean very good).
'an'+'ace'='anace'
'pa' placed around 'anace' is 'PANACEA'.
(Other definitions for panacea that I've seen before include "Hypothetical universal remedy" , "that'll solve everything" , "Cure for all ills" , "that will cure anything" , "Remedy for all kinds of diseases or troubles" .)