Appear to notice Mike (4)
I believe the answer is:
seem
'appear' is the definition.
(I know that seem is a more specific form of appear)
'notice mike' is the wordplay.
'notice' becomes 'see' (notice can mean to spot or see).
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'see'+'m'='SEEM'
'to' acts as a link.
(Other definitions for seem that I've seen before include "Appear, look" , "Appear to the eye" , "Come across as" , "Appear, give impression of being" .)