Bill — money, in manner of speaking (6)
I believe the answer is:
accent
'manner of speaking' is the definition.
(accent is a kind of manner of speaking)
'bill money' is the wordplay.
'bill' becomes 'ac'.
'money' becomes 'cent' (I've seen this before).
'ac'+'cent'='ACCENT'
'in' acts as a link.
(Other definitions for accent that I've seen before include "Distinctive local way of speaking" , "Special emphasis" , "Distinctive manner of oral expression" , "Place stress on, say a syllable" , "Mark used to indecate pronunciation" .)