Herb in bearnaise sauce (8)
I believe the answer is:
tarragon
'herb in bearnaise sauce' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tarragon that I've seen before include "cooking ingredient" , "Strangely arrogant herb" , "leaves" , "cooks may use it" , "seasoning" .)