Scales of charges Spain introduced for third of Catalans (7)
I believe the answer is:
indices
'scales of charges' is the definition.
'indices' can be an answer for 'scales'. I'm not sure about the 'of charges' bit.
'spain introduced for third of catalans' is the wordplay.
I cannot quite see how this works, but
'spain' could be 'es' (es is an abbreviation for Spain) and 'es' is found in the answer.
The remaining letters 'indic' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for indices that I've seen before include "Files" , "Alphabetical listings" , "Indicators; references" , "Catalogues" , "Mathematical symbols denoting powers" .)