Release without charge (4)
I believe the answer is:
free
This clue is a double definition.
'release' is the first definition.
(synonyms)
'without charge' is the second definition.
(sold at no cost)
(Other definitions for free that I've seen before include "with no toll demanded?" , "Gratis, for nothing" , "Reef (anag.)" , "Not busy" , "Unfettered" .)