Number Ten ace has it refurbished (11)
I believe the answer is:
anaesthetic
'number' is the definition.
(something which 'numbs' you)
'ten ace has it refurbished' is the wordplay.
'refurbished' indicates anagramming the letters.
'ten'+'ace'+'has'+'it'='tenacehasit'
'tenacehasit' with letters rearranged gives 'ANAESTHETIC'.
(Other definitions for anaesthetic that I've seen before include "Number of bodies - can hesitate (anag)" , "Knockout drug" , "A number of theatres" , "painkiller" , "Drug that causes temporary loss of feeling" .)