Heal so as to make robust (4)

I believe the answer is:

hale

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'robust' is the definition.
(in good health)

'heal so as to' is the wordplay.
'heal' can be anagrammed to 'HALE'.
Though, I am unsure how this is indicated.

'make' acts as a link.

Can you help me to learn more?

(Other definitions for hale that I've seen before include "Well" , "Strong and healthy" , "Healthy and robust" , "Sound of body" , "Showing vigorous good health" .)

I've seen this clue in the Evening Standard.

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