Fashionable to communicate account (7)
I believe the answer is:
invoice
'account' is the definition.
('invoice' can be a synonym of 'account')
'fashionable to communicate' is the wordplay.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'to communicate' becomes 'voice'.
'in'+'voice'='INVOICE'
(Other definitions for invoice that I've seen before include "Demand for sum due" , "Statement of money to be paid" , "Give account" , "Statement of account" , "Demand for payment" .)