Repeat charge applied to unprotected sites (7)
I believe the answer is:
iterate
'repeat' is the definition.
('iterate' can be a synonym of 'repeat')
'charge applied to unprotected sites' is the wordplay.
'charge' becomes 'rate' (rate is a kind of charge**).
'applied to' says to put letters next to each other.
'unprotected' means to look at the middle letters.
The middle letters of 'sites' are 'ite'.
'rate' after 'ite' is 'ITERATE'.
(Other definitions for iterate that I've seen before include "Repeat, state again" , "Recapitulate" , "Utter or perform repeatedly" , "Say again, repeat" , "State repeatedly, say again" .)