Highlight account over money (6)
I believe the answer is:
accent
'highlight' is the definition.
(I've seen this in another clue)
'account over money' is the wordplay.
'account' becomes 'ac' (abbreviation for account).
'over' says to put letters next to each other.
'money' becomes 'cent' (eg denomination of dollars).
'ac'+'cent'='ACCENT'
(Other definitions for accent that I've seen before include "it could be grave" , "Particular emphasis" , "A diacritic mark" , "It could be acute" , "Stress - manner of speech" .)