Packing ring with a little current inside (7)
I believe the answer is:
tamping
'packing' is the definition.
('tamp' can be a synonym of 'pack')
'ring with a little current inside' is the wordplay.
'ring' becomes 'ting' (I have seen 'Sharp ring ' mean 'ting' so perhaps 'ring' could also mean 'ting').
'with' indicates putting letters inside.
'a little current inside' becomes 'amp' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ting' going around 'amp' is 'TAMPING'.
Can you help me to learn more?
(Other definitions for tamping that I've seen before include "Firmly ramming down to consolidate" , "filling a hole" .)