Telephoned by a drunk? That's unacceptable (6,3,4)
I believe the answer is:
beyond the pale
'unacceptable' is the definition.
(I've seen this before)
'telephoned by a drunk?' is the wordplay.
'drunk?' is an anagram indicator (I've seen 'drunk' mean this).
'telephoned'+'by'+'a'='telephonedbya'
'telephonedbya' with letters rearranged gives 'BEYOND THE PALE'.
'that's' acts as a link.
(Other definitions for beyond the pale that I've seen before include "Unacceptable (behaviour)" , "Unthinkable" , "Not understood by untanned people" , "Totally unacceptable" , "to be completely colourless?" .)