Be still turning up in a tasty concoction (4,3)
I believe the answer is:
stay put
'be still' is the definition.
(thesaurus)
'turning up in a tasty concoction' is the wordplay.
'turning' says the letters should be written backwards.
'in' means one lot of letters goes inside another.
'concoction' is an anagram indicator.
'up' backwards is 'pu'.
'tasty' anagrammed gives 'stayt'.
'pu' inserted inside 'stayt' is 'STAY PUT'.
(Other definitions for stay put that I've seen before include "Remain in one place" , "Remain in place, don't move" , "Stick around" , "Informally, don't move - remain in situ" , "Remain unmoving" .)