Crossword Genius

Queen to withdraw for this reason? (4)

Ross

I believe the answer is:

ergo

'for this reason?' is the definition.
(thesaurus)

'queen to withdraw' is the wordplay.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'to withdraw' becomes 'go'.
'er'+'go'='ERGO'

(Other definitions for ergo that I've seen before include "as a consequence" , "It follows" , "'Cogito, ---- sum'" , "Therefore (Latin)" , "so philosopher wrote in Latin" .)

I've seen this clue in The Guardian.
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