Mike is stopping certain suspect (7)
I believe the answer is:
surmise
'suspect' is the definition.
(I know that suspect can be written as surmise)
'mike is stopping certain' is the wordplay.
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'stopping' indicates putting letters inside (stopping can mean blocking a gap).
'certain' becomes 'sure' (synonyms).
'm'+'is'='mis'
'mis' put inside 'sure' is 'SURMISE'.
(Other definitions for surmise that I've seen before include "Speculate about misuser" , "Hazard a guess" , "Suppose without evidence" , "Make a conjecture" , "Conjecture; Cortez's men's was wild (Keats)" .)