Draw on unknown fabric (5)

I believe the answer is:

lurex

'fabric' is the definition.
(lurex is a type of fabric)

'draw on unknown' is the wordplay.
'draw' becomes 'lure' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'unknown' becomes 'x' (algebra).
'lure'+'x'='LUREX'

(Another definition for lurex that I've seen is " flashing cloth".)

I've seen this clue in The Independent.

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