Crossword Genius

Flyer promoting Icelandic dairy product with custom jams (9)

Ross

I believe the answer is:

skywriter

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

'flyer' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see a link between them that I can't see?

'promoting icelandic dairy product with custom jams' is the wordplay.
I cannot quite understand how this works, but
'with' could be 'w' (short for with) and 'w' is found in the answer.
'custom' could be 'rite' (rite is a kind of custom) and 'rite' is found in the answer.
The remaining letters 'skyr' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for skywriter that I've seen before include "author of heavenly words" , "Aerial advertiser using smoke" , "Pilot creating a message with smoke trails" .)

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