Crossword Genius

Class, one lacking in brilliance (5)

Ross

I believe the answer is:

genus

'class' is the definition.
(thesaurus)

'one lacking in brilliance' is the wordplay.
'one' becomes 'i' (Roman numeral).
'lacking in' suggests deleting specific letters.
'brilliance' becomes 'genius' ('genius' can be a synonym of 'brilliance').
'genius' with 'i' taken away is 'GENUS'.

(Other definitions for genus that I've seen before include "Latin class?" , "Taxonomic grouping" , "Category between family and species" , "Taxonomic class between family and species" , "Taxonomic category above species" .)

I've seen this clue in The Times.
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