Difficulty getting to the top for unqualified head (9)

I believe the answer is:

sheerness

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'difficulty getting to the top' is the definition.
I can't tell whether this defines the answer.

'unqualified head' is the wordplay.
'unqualified' becomes 'sheer' (I've seen this before).
'head' becomes 'ness' (type of geographical point).
'sheer'+'ness'='SHEERNESS'

'for' is the link.

Can you help me to learn more?

(Other definitions for sheerness that I've seen before include "Perpendicularity; Isle of Sheppey town" , "Site of former naval dockyard in Isle of Sheppey" , "port" , "Kent resort" , "Kentish Town" .)

I've seen this clue in The Guardian.

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