Insect makes shade before ruler (6,7)

I believe the answer is:

purple emperor

I'm a little stuck... Click here to teach me more about this clue!

'insect' is the definition.
(purple emperor is a kind of insect)

'shade before ruler' is the wordplay.
'shade before' becomes 'purple' (I've seen this before. I am not sure about the 'before' bit.).
'ruler' becomes 'emperor' (emperor is a kind of ruler).
'purple'+'emperor'='PURPLE EMPEROR'

'makes' is the link.

Can you help me to learn more?

(Other definitions for purple emperor that I've seen before include "One flapping about" , "Large British butterfly" , "Insect" , "Flyer" , "Butterfly (appropriately coloured)" .)

I've seen this clue in The Daily Express.

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