Forbidding earth to be called dirt (5)

I believe the answer is:

grime

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'called dirt' is the definition.
'grime' can be an answer for 'dirt' ('grime' can be a synonym of 'dirt'). I am not sure about the 'called' bit.

'forbidding earth' is the wordplay.
'forbidding' becomes 'grim' (I've seen this before).
'earth' becomes 'e'.
'grim'+'e'='GRIME'

'to be' acts as a link.

Can you help me to learn more?

(Other definitions for grime that I've seen before include "Muck" , "Ingrained dirt" , "an ingrained phenomenon" , "Dirt, grease" , "Soot" .)

I've seen this clue in the Evening Standard.

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