Utter nothing in between (8)
I believe the answer is:
thorough
'utter' is the definition.
(I've seen this before)
'nothing in between' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'in' is an insertion indicator.
'between' becomes 'through'.
'o' placed within 'through' is 'THOROUGH'.
(Other definitions for thorough that I've seen before include "Total - painstaking - in-depth" , "Rigorous" , "Echaustive, complete" , "Absolute, utter" , "Painstaking; absolute" .)