Philip and Edward have to stop talking (4,4)
I believe the answer is:
pipe down
'stop talking' is the definition.
(I've seen this before)
'philip and edward have' is the wordplay.
'philip' becomes 'pip' (can be a nickname for Philip).
'and' means one lot of letters go next to another.
'edward' becomes 'ed'.
'have' becomes 'own' ('own' can be a synonym of 'have').
'pip'+'ed'+'own'='PIPE DOWN'
'to' is the link.
(Other definitions for pipe down that I've seen before include "Shut up!" , "make less noise" , "Stop talking" , "Sh!" , "Be quiet!" .)