Acquit without costs? (4,2,6)
I believe the answer is:
free of charge
'acquit without costs?' is the definition.
I can't tell whether this definition defines the answer.
'without costs?' is the wordplay.
'without' becomes 'free of' (I've seen this in another clue).
'costs?' becomes 'charge' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'freeof'+'charge'='FREE OF CHARGE'
Can you help me to learn more?
(Other definitions for free of charge that I've seen before include "Gratis" , "On the house" .)