A shortage? Oh dear! (5)

I believe the answer is:

alack

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'oh dear' is the definition.
I can't tell whether this defines the answer.

'a shortage?' is the wordplay.
'shortage?' becomes 'lack' (shortage is a kind of lack).
'a'+'lack'='ALACK'

Can you help me to learn more?

(Other definitions for alack that I've seen before include "expression of regret" , "unfortunately" , "I mourn" , "Previously expressed regret" , "Old expression of dismay" .)

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

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