Flood shown in new film (7)
I believe the answer is:
freshet
'flood' is the definition.
(thesaurus)
'new film' is the wordplay.
'new' becomes 'fresh' ('fresh' can be similar in meaning to 'new').
'film' becomes 'et'.
'fresh'+'et'='FRESHET'
'shown in' acts as a link.
(Other definitions for freshet that I've seen before include "flood" , "Stream or rush of water entering the sea" , "He frets over stream running into sea" .)