Charge about river unchecked (4)
I believe the answer is:
free
'unchecked' is the definition.
(thesaurus)
'charge about river' is the wordplay.
'charge' becomes 'fee' (fee is a kind of charge).
'about' means one lot of letters goes inside another.
'river' becomes 'r' (abbreviation for river).
'fee' going around 'r' is 'FREE'.
(Other definitions for free that I've seen before include "Sewn-on trimming" , "Complimentary" , "Generous, rid, available" , "Unfettered" , "Release; gratis" .)