Casual worker starts to unpick really appetising Japanese dish (7)
I believe the answer is:
tempura
'japanese dish' is the definition.
(I've seen this before)
'casual worker starts to unpick really appetising' is the wordplay.
'casual worker' becomes 'temp' (short-term or temporary worker).
'starts to' says to take the initial letters.
The first letters of 'unpick really appetising' is 'ura'.
'temp'+'ura'='TEMPURA'
(Other definitions for tempura that I've seen before include "Deep-fried in batter, Japanese-style" , "Japanese food fried in batter" , "Foreign dish" , "Vegetables and seafood deep-fried in batter" , "Japanese dish fried in batter" .)