Flawless proposal, hitting all the right notes (7,5)
I believe the answer is:
perfect pitch
'hitting all the right notes' is the definition.
I can't tell whether this defines the answer.
'flawless proposal' is the wordplay.
'flawless' becomes 'perfect' (similar in meaning).
'proposal' becomes 'pitch' (I am not sure about this - if you are sure you should believe this answer much more).
'perfect'+'pitch'='PERFECT PITCH'
Can you help me to learn more?
(Other definitions for perfect pitch that I've seen before include "Musical talent (one appreciated by batsmen?)" , "Ability to recognise musical notes by ear - ideal batting surface?" , "Ability to identify notes" , "Ability to recognise notes accurately" , "Note talent" .)