Bank's reply initially appallingly derisive (9)
I believe the answer is:
riverside
'bank's' is the definition.
(riverside is a kind of bank)
'reply initially appallingly derisive' is the wordplay.
'initially' suggests taking the first letters.
'appallingly' is an anagram indicator (I've seen this in other clues).
The initial letter of 'reply' is 'r'.
'derisive' anagrammed gives 'iverside'.
'r'+'iverside'='RIVERSIDE'
(Other definitions for riverside that I've seen before include "Area along, say, the Thames" , "Bank" .)