Best time for greeting Doris (6)

I believe the answer is:

heyday

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'best time' is the definition.
(I've seen this before)

'greeting doris' is the wordplay.
'greeting' becomes 'hey' (I can't justify this - if you can you should believe this answer much more).
'doris' becomes 'Day' (actress Doris Day is an example).
'hey'+'day'='HEYDAY'

'for' is the link.

Can you help me to learn more?

(Other definitions for heyday that I've seen before include "The time of greatest success or prosperity" , "Period of greatest success and popularity" , "Boom time" , "Prime time?" , "Time of maximum prosperity" .)

I've seen this clue in the Sydney Morning Herald.

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