Reply being tripe so appalling (7)
I believe the answer is:
riposte
'reply' is the definition.
(I know that riposte is a type of reply)
'tripe so appalling' is the wordplay.
'appalling' is an anagram indicator (an appalling spelling).
'tripe'+'so'='tripeso'
'tripeso' is an anagram of 'RIPOSTE'.
'being' acts as a link.
(Other definitions for riposte that I've seen before include "Counter-thrust" , "Smart reply" , "Reply, response" , "Fencer's counterattack" , "Reply, retort" .)