Sober gowns (5)

I believe the answer is:

robes

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

'gowns' is the definition.
('robe' can be a synonym of 'gown')

'sober' is the wordplay.
'sober' can be anagrammed to 'ROBES'.
But, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for robes that I've seen before include "'The 19 across 1 across' of the French Revolution" , "Attire" , "Gowns" , "Long loose flowing garments" , "trappings of office?" .)

I've seen this clue in The Irish Independent.

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