Old newsman goes round Open University with a messenger (7)
I believe the answer is:
courier
'messenger' is the definition.
(I know that messenger can be written as courier)
'old newsman goes round open university' is the wordplay.
'old newsman' becomes 'crier' (I can't explain this - if you can you should give a lot more credence to this answer).
'goes round' indicates putting letters inside.
'open university' becomes 'OU'.
'crier' going around 'ou' is 'COURIER'.
'with a' is the link.
Can you help me to learn more?
(Other definitions for courier that I've seen before include "Delivery messenger" , "Messenger, often on a motorbike" , "guide for tourists" , "Messenger carrying papers etc, perhaps on motorbike" , "Message-carrier" .)