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 in reverse.
'in' is an insertion indicator.
'concoction' is an anagram indicator.
'up' back-to-front is 'pu'.
'tasty' with letters rearranged gives 'stayt'.
'pu' going into '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" .)