River between Great Lakes (7)
I believe the answer is:
niagara
'river between great lakes' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for niagara that I've seen before include "Great waterfalls on Canadian-US border" , "US/Canadian falls" , "Waterfall at Iran aga" , "Famous waterfalls" , "River linking Lakes Ontario and Erie" .)