Mike with best friend's first computer (7)
I believe the answer is:
palmtop
'computer' is the definition.
(I've seen this before)
'mike with best friend's first' is the wordplay.
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' is a charade indicator (letters next to each other).
'best friend' becomes 'pal' (I've seen this in another clue).
'first' becomes 'top' (top can mean the best or first).
'm' after 'pal' is 'palm'.
'palm'+'top'='PALMTOP'
(Other definitions for palmtop that I've seen before include "PC" , "Hand-held computer" , "Greeting" .)