Insensitive digit has no hesitation (4)

I believe the answer is:

numb

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'insensitive' is the definition.
(synonyms)

'digit has no hesitation' is the wordplay.
'digit' becomes 'b' (I can't explain this - if you can you should believe this answer much more).
'has' means one lot of letters go next to another.
'no' becomes 'n' (common abbreviation).
'hesitation' becomes 'um' (um is said in hesitation).
'n'+'um'='num'
'b' after 'num' is 'NUMB'.

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(Other definitions for numb that I've seen before include "Deadened, desensitised" , "Lacking feeling" , "Without feeling" , "Deaden" , "Stupefied; unfeeling" .)

I've seen this clue in The Daily Express.

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