Force used after breaking barrier (9)
I believe the answer is:
waterfall
'force' is the definition.
(thesaurus)
'used after breaking barrier' is the wordplay.
'used' is an anagram indicator.
'breaking' is an insertion indicator.
'barrier' becomes 'wall' (I've seen this before).
'after' is an anagram of 'terfa'.
'terfa' going within 'wall' is 'WATERFALL'.
(Other definitions for waterfall that I've seen before include "Perpendicular descent of a river" , "One of the aqueous drops" , "source of power, possibly a force in the north" , "Steep descent of a river" , "Cataract" .)