Reply from central address that is receiving letters (7)
I believe the answer is:
riposte
'reply' is the definition.
(I know that riposte is a type of reply)
'central address that is receiving letters' is the wordplay.
'central' says to take the centre.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'receiving' is an insertion indicator.
'letters' becomes 'post' (letters in the mail or post).
The centre of 'address' is 'r'.
'ie' going around 'post' is 'iposte'.
'r'+'iposte'='RIPOSTE'
'from' acts as a link.
(Other definitions for riposte that I've seen before include "Quick clever reply" , "Fencing counterattack" , "Quick retort or return thrust in fencing" , "Fencer's counterattack" , "Smart reply" .)