Discharge former partner in robust health (6)

I believe the answer is:

exhale

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'discharge' is the definition.
(I've seen this before)

'former partner in robust health' is the wordplay.
'former partner' becomes 'ex'.
'in robust health' becomes 'hale' (I can't explain this - if you can you should give a lot more credence to this answer).
'ex'+'hale'='EXHALE'

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(Other definitions for exhale that I've seen before include "Discharge" , "Give out" , "produce emissions" , "expire" , "Breathe out" .)

I've seen this clue in The Times.

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