An upper class girl takes it in charge (5)
I believe the answer is:
debit
'charge' is the definition.
(I know that charge is a more specific form of the action debit)
'an upper class girl takes it in' is the wordplay.
'an upper class' becomes 'eb' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'girl' becomes 'di'.
'takes' is a charade indicator (letters next to each other).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'in' indicates putting letters inside.
'di'+'t'='dit'
'eb' inserted into 'dit' is 'DEBIT'.
Can you help me to learn more?
(Other definitions for debit that I've seen before include "Make entry in accounts of sum owed" , "Opposite of credit" , "Accounting entry showing sum owing" , "Sum owing (in accounts)" , "Take money away from" .)