Certain Mike is being included? A guess (7)
I believe the answer is:
surmise
'a guess' is the definition.
(synonyms)
'certain mike is being included?' is the wordplay.
'certain' becomes 'sure' (synonyms).
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'being included?' means one lot of letters goes inside another.
'm'+'is'='mis'
'sure' going around 'mis' is 'SURMISE'.
(Other definitions for surmise that I've seen before include "Presume -- rue miss (anag)" , "Conjecture; Cortez's men's was wild (Keats)" , "Imagine" , "Speculate about misuser" , "Guess, conjecture" .)