Showing debility - a pick-me-up is needed (6)

I believe the answer is:

atonic

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'showing debility a pick-me-up is needed' is the definition.
I can't tell whether this defines the answer.

'a pick-me-up is needed' is the wordplay.
'pick-me-up' becomes 'tonic' (I've seen this before).
'is needed' means one lot of letters go next to another.
'a'+'tonic'='ATONIC'

Can you help me to learn more?

(Other definitions for atonic that I've seen before include "(In poetry) unaccented" , "Unstressed (poetry)" .)

I've seen this clue in The Irish Independent.

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