Dead centre, miles inside (4)
I believe the answer is:
numb
'dead' is the definition.
(thesaurus)
'centre miles inside' is the wordplay.
'centre' becomes 'nub' (I've seen this before).
'miles' becomes 'm' (common abbreviation).
'inside' indicates putting letters inside.
'nub' going around 'm' is 'NUMB'.
(Other definitions for numb that I've seen before include "Lacking feeling" , "Deadened, desensitised" , "Deprived of feeling" , "Frozen" , "Feeling nothing" .)