Strange gap in Nell’s wall surfacing (9)

I believe the answer is:

panelling

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

'wall surfacing' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'strange gap in nell's' is the wordplay.
'strange' indicates an anagram.
'gap'+'in'+'nell'='gapinnell'
'gapinnell' is an anagram of 'PANELLING'.

Can you help me to learn more?

I've seen this clue in The Times.

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