A state charge say for nails (5)
I believe the answer is:
'for nails' is the definition.
(tack is a kind of nail)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tacks that I've seen before include "Small broad-headed nails" , "Short nails" , "Changes course" , "Approaches" , "a few points" .)