Excellent reason to start with show (3)
I believe the answer is:
air
'show' is the definition.
(both can mean broadcast)
'excellent reason to start' is the wordplay.
'excellent' becomes 'ai'.
'to start' indicates taking the first letters.
The initial letter of 'reason' is 'r'.
'ai'+'r'='AIR'
'with' is the link.
(Other definitions for air that I've seen before include "Vital thing" , "Broadcast; express" , "Atmosphere surrounding us" , "character" , "Display" .)