Channels in sea area around island (5)
I believe the answer is:
media
'channels' is the definition.
(I have seen 'Channels of communication ' mean 'media' so perhaps 'channels' could also mean 'media')
'sea area around island' is the wordplay.
'sea' becomes 'med' (short for Mediterranean).
'area' becomes 'a' (maths abbreviation).
'around' is an insertion indicator.
'island' becomes 'i' (geographical abbreviation).
'med'+'a'='meda'
'meda' going around 'i' is 'MEDIA'.
'in' is the link.
(Other definitions for media that I've seen before include "Press, TV etc" , "means for spreading news" , "Means of mass communication" , "Reporters" , "Press, TV, radio" .)