Modem/AI link-up incorporates communication method (5)
I believe the answer is:
'communication method' is the definition.
'modemai link-up incorporates' is the wordplay.
'incorporates' indicates a hidden word.
'EMAIL' can be found hidden inside 'modemai link up'.
(Other definitions for email that I've seen before include "Digital message" , "Electronic communication" , "Spam perhaps" , "Send one online" , "Messages between computer terminals" .)