In honest fashion on account of being with bank (9)
I believe the answer is:
sincerely
'in honest fashion on account of being with bank' is the definition.
I can't judge whether this definition defines the answer.
'on account of being with bank' is the wordplay.
'on account of' becomes 'since' (I've seen this in another clue).
'being with' means one lot of letters go next to another.
'bank' becomes 'rely' (to bank on something is to rely on it).
'since'+'rely'='SINCERELY'
Can you help me to learn more?
(Other definitions for sincerely that I've seen before include "without hypocrisy" , "Not showing any deceit" , "the last word before signing" , "In good faith" , "Really" .)