Falls once more backwards gripping a bar's end (7)
I believe the answer is:
niagara
'falls' is the definition.
(thesaurus)
'once more backwards gripping a bar's end' is the wordplay.
'once more' becomes 'again' ('again' can be a synonym of 'once more'**).
'backwards' is a reversal indicator.
'gripping' means one lot of letters goes inside another.
'end' says to take the final letters.
The final letter of 'bar' is 'r'.
'again' written backwards gives 'niaga'.
'a'+'r'='ar'
'niaga' enclosing 'ar' is 'NIAGARA'.
(Other definitions for niagara that I've seen before include "N. American waterfall" , "Canadian waterfall" , "1953 Marilyn Monroe film noir thriller" , "North American river with famous falls" , "& 22 Down North American cascade" .)