Absolutely empty lavatory is lethal (6)

I believe the answer is:

deadly

'is lethal' is the definition.
(synonyms)

'absolutely empty lavatory' is the wordplay.
'absolutely' becomes 'dead' (synonyms).
'empty' means to remove the middle letters.
'lavatory' with its middle taken out is 'ly'.
'dead'+'ly'='DEADLY'

(Other definitions for deadly that I've seen before include "No small bore" , "Lethal, could be fatal" , "sniper aspires to be" , "Belladonna" , "There are seven such sins" .)

I've seen this clue in The Guardian.

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