Herb for guru (4)
I believe the answer is:
sage
I believe this is a double definition.
'herb' is the first definition.
(I know that Sage is a type of herb)
'guru' is the second definition.
(synonyms)
'for' acts as a link.
(Other definitions for sage that I've seen before include "___ and onion" , "Aromatic herb" , "Wise man - flavoursome plant" , "Velvety-leaved herb" , "Savant" .)