An airport show's over - this might open up a channel? (8)
I believe the answer is:
laxative
'this might open up a channel?' is the definition.
(a laxative might open up the digestive system)
'an airport show's over' is the wordplay.
'an airport' becomes 'lax' (abbreviation for Los Angeles International Airport).
'show' becomes 'evita' (musical).
'over' shows that the letters should be reversed in order.
'evita' written backwards gives 'ative'.
'lax'+'ative'='LAXATIVE'
(Other definitions for laxative that I've seen before include "Purgative, loosener" , "Medicine for constipation" , "Aperient medicine" .)