Stein's original potato dish is a hit (5)
I believe the answer is:
smash
'a hit' is the definition.
(smash is a kind of hit)
'stein's original potato dish' is the wordplay.
'original' says to take the initial letters.
'potato dish' becomes 'mash' (I've seen this before).
The first letter of 'stein' is 's'.
's'+'mash'='SMASH'
'is' acts as a link.
(Other definitions for smash that I've seen before include "Shatter violently" , "Overarm volley" , "Break noisely into pieces" , "- - and grab" , "defeat" .)