Muddled account accepted by one following (7)
I believe the answer is:
inexact
'muddled' is the definition.
(thesaurus)
'account accepted by one following' is the wordplay.
'account' becomes 'ac'.
'accepted by' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'following' becomes 'next' ('next' can be a synonym of 'following').
'i'+'next'='inext'
'ac' put into 'inext' is 'INEXACT'.
(Other definitions for inexact that I've seen before include "Vague" , "Not quite accurate" , "Not precise, approximate" , "Rough" , "Not entirely accurate" .)