Don't stop dupe ringing Henry in East end (5,2)
I believe the answer is:
carry on
'don't stop' is the definition.
(I've seen this before)
'dupe ringing henry in east end' is the wordplay.
'dupe' becomes 'con' (I've seen this before).
'ringing' means one lot of letters goes inside another.
'henry in east end' becomes 'arry' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'con' enclosing 'arry' is 'CARRY-ON'.
Can you help me to learn more?
(Other definitions for carry on that I've seen before include "Continue - make a fuss" , "Misbehave badly" , "kind of case one handles personally" , "Continue like British comedy films?" , "Don't give up" .)