A sainted monarch's flower? (5)

I believe the answer is:

aster

'flower?' is the definition.
(type of flower)

'a sainted monarch's' is the wordplay.
'sainted' becomes 'st'.
'monarch' becomes 'er' (abbreviation for Elizabeth Regina, British Queen).
'a'+'st'+'er'='ASTER'

(Other definitions for aster that I've seen before include "Michaelmas daisy genus" , "Flower of the daisy family - rates (anag)" , "(Starlike) flower" , "Kind of daisy" , "Tears about bright flower" .)

I've seen this clue in the Evening Standard.

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