See me in repeat broadcast that’s diffuse (8)
I believe the answer is:
permeate
'diffuse' is the definition.
('permeate' can be a synonym of 'diffuse')
'see me in repeat broadcast' is the wordplay.
'in' indicates putting letters inside.
'broadcast' is an anagram indicator.
'repeat' anagrammed gives 'perate'.
'me' inserted within 'perate' is 'PERMEATE'.
'that's' is the link.
(Other definitions for permeate that I've seen before include "Spread right through" , "Pass through" , "Soak through" , "Seep through" , "Suffuse" .)