A sore head needs treating with it! (10)

I believe the answer is:

tenderness

I'm a little stuck... Click here to teach me more about this clue!

'treating with it' is the definition.
I can't tell whether this defines the answer.

'a sore head' is the wordplay.
'a sore' becomes 'tender' (I've seen this in another clue).
'head' becomes 'ness' (ness is a headland).
'tender'+'ness'='TENDERNESS'

'needs' is the link.

Can you help me to learn more?

(Other definitions for tenderness that I've seen before include "Gentleness, sensitivity" , "Gentle quality" , "Heart" , "sore?" , "Compassion" .)

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

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