We'll have no more of that! Plug up the hole (4,2)
I believe the answer is:
stop it
'we'll have no' is the definition.
I know nothing about this answer so I can't judge whether this works.
'of that plug up the hole' is the wordplay.
'of' becomes 'o''.
'that plug' means one lot of letters goes inside another.
'up' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'hole' becomes 'pit' (a pit is a large hole).
's'+'t'+'pit'='stpit'
'o' going into 'stpit' is 'STOP IT'.
'more' acts as a link.
Can you help me to learn more?
(Other definitions for stop it that I've seen before include "Desist!" , "Don't" .)