River roaring furiously, not half deep (3,6)
I believe the answer is:
rio grande
'river' is the definition.
(Rio Grande is an example)
'roaring furiously not half deep' is the wordplay.
'furiously' indicates an anagram.
'not half' means to take half the letters.
'deep' with half the letters taken is 'de'.
'roaring' is an anagram of 'riogran'.
'riogran'+'de'='RIO GRANDE'
(Other definitions for rio grande that I've seen before include "banker" , "Great river bordering USA and Mexico" , "River boundary between the US and Mexico" , "Long river" , "Waterway rising in Colorado" .)