For these containers there are a number of charges (6)
I believe the answer is:
crates
'for these containers' is the definition.
(crate is a kind of container)
'there are a number of charges' is the wordplay.
I cannot quite see how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is present in the answer.
'number' could be 'e' (e is a kind of number) and 'e' is found within the answer.
The remaining letters 'crts' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for crates that I've seen before include "Rough wooden boxes" , "Jalopies" , "Packing cases" , "Boxes for shipping goods" .)