Walk out hosting Good Morning Britain show (7)
I believe the answer is:
exhibit
'show' is the definition.
(I know that exhibit is a kind of show)
'walk out hosting good morning britain' is the wordplay.
'walk out' becomes 'exit' (I've seen this in another clue).
'hosting' means one lot of letters goes inside another (inserted letters are welcomed in or hosted).
'good morning' becomes 'hi' (I can't justify this - if you can you should give a lot more credence to this answer).
'britain' becomes 'B' (common abbreviation as in GB).
'hi'+'b'='hib'
'exit' placed around 'hib' is 'EXHIBIT'.
Can you help me to learn more?
(Other definitions for exhibit that I've seen before include "Manifest" , "Publicly display" , "Object on formal public display" , "parade" , "Show - piece of evidence in court" .)