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' indicates an anagram.
'up' written backwards gives 'pu'.
'tasty' is an anagram of 'stayt'.
'pu' going 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" .)