Crossword Genius

Sort of square rings on top of that (3)

Ross

I believe the answer is:

too

'on top of that' is the definition.
(I've seen this before)

'sort of square rings' is the wordplay.
'sort of square' becomes 't' (a T-Square is a technical drawing instrument).
'rings' becomes 'oo' (multiple circles).
't'+'oo'='TOO'

(Other definitions for too that I've seen before include "What a pity!" , "On top - also" , "As well; in addition" , "Excessively" , "Unduly" .)

I've seen this clue in The Times.
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