Waves and cheers to welcome star on unfinished film (8)
I believe the answer is:
tsunamis
'waves' is the definition.
(I know this)
'star on unfinished film' is the wordplay.
'star' becomes 'sun' (the Sun is a star).
'on' indicates putting letters inside.
'unfinished film' becomes 'tamis' (I am not sure about this - if you are sure you should believe this answer much more).
'sun' inserted within 'tamis' is 'TSUNAMIS'.
'and cheers to welcome' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tsunamis that I've seen before include "Huge destructive waves" , "catastrophes" , "Large ocean waves caused by underwater earthquakes" , "Destructive sea waves" , "Violent sea waves" .)