Found in a monastery garden? (5)

I believe the answer is:

aster

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'garden?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'found in a monastery' is the wordplay.
'found in' says the answer is hidden in the clue.
'ASTER' is hidden within 'monastery'.

Can you help me to learn more?

(Other definitions for aster that I've seen before include "Large daisy" , "Daisy-like garden flower" , "eg Michaelmas daisy" , "Flowering plant; tares (anag.)" , "Flower of the daisy family - rates (anag)" .)

I've seen this clue in The Globe and Mail.

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