Iridescent Hanson uniform folded near fifth button (7)

I believe the answer is:

opaline

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'iridescent' is the definition.
(I know that iridescent can be written as opaline)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for opaline that I've seen before include "white!" , "like a stone" , "Opaquish glass; iridescent" , "Semi-translucent glass" , "milky" .)

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

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