Colouring agent showed up in a stable diet in the golden years (6)
I believe the answer is:
heyday
'the golden years' is the definition.
The definition and answer can be both related to time as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'colouring agent showed up in a stable diet' is the wordplay.
'colouring agent' becomes 'dye' (I've seen this before).
'showed up' shows that the letters should be reversed in order (I've seen 'shown up' mean this).
'in' means one lot of letters goes inside another.
'a stable diet' becomes 'hay' (I've seen this in another clue).
'dye' back-to-front is 'eyd'.
'eyd' placed within 'hay' is 'HEYDAY'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for heyday that I've seen before include "Highest period in someone's career" , "Period of greatest success and popularity" , "Period of one's greatest productivity" , "golden age" , "The flush of vigour, health etc." .)