Forming bands visible in horizon, almost (5)

I believe the answer is:

zonal

'forming bands' is the definition.
(making zones or bands)

'visible in horizon almost' is the wordplay.
'visible in' indicates the answer is hidden within the clue.
'ZONAL' is hidden within 'horizon almost'.

(Other definitions for zonal that I've seen before include "Relating to region" , "Like area" , "Regional" , "Of a distinctive location" , "Pertaining to defined regions" .)

I've seen this clue in The Guardian.

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