This unfortunately smashes (4)
I believe the answer is:
hits
'smashes' is the definition.
('hit' can be a synonym of 'smash')
'this unfortunately' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'this' anagrammed gives 'HITS'.
(Other definitions for hits that I've seen before include "Top pops" , "welcome in the theatre world?" , "The sort of strikes" , "Pop successes" , "that please the public?" .)