Spell single word for Scrabble's elementary rule (8,3)

I believe the answer is:

periodic law

'elementary rule' is the definition.
(rule relating to elements on the Periodic Table)

'spell single word for scrabble's' is the wordplay.
'spell' becomes 'period' (I've seen this before).
'single' becomes 'i' (one).
'word for scrabble' becomes 'claw' (claw and scrabble can be synonyms).
'period'+'i'+'claw'='PERIODIC LAW'

I've seen this clue in The Guardian.

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