Ready to receive East German response (7)
I believe the answer is:
Here is my best explanation:
'response' is the definition.
(riposte is a kind of response)
'ready to receive east german' is the subsidiary indication.
'ready' becomes 'ripe' ('ripe' can be similar in meaning to 'ready').
'to receive' indicates putting letters inside.
'east german' becomes 'ost'.
'ripe' enclosing 'ost' is 'riposte'.
(Other definitions for riposte that I've seen before include "Fencer's counterattack", "Witty retort", "Repartee; quick thrust (fencing)", "Quick retort or return hit in fencing", "Witty reply", "Retort", "Smart reply", "Snappy comeback", "Fencing counterattack" and "Witty comeback".)