Costs of Queen's son good for Left (7)
I believe the answer is:
charges
'costs' is the definition.
(charge is a kind of cost)
'queen's son good for left' is the wordplay.
I cannot really understand how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is found within the answer.
'good' could be 'g' (abbreviation) and 'g' is found within the answer.
'queen' could be 'r' (abbreviation for regina, e.g. in ER ) and 'r' is present in the answer.
This explanation may well be incorrect...
'of' acts as a link.
Can you help me to learn more?
(Other definitions for charges that I've seen before include "Expenses" , "Accusations of guilt" , "Accuses" , "Formal accusations" .)