Lear's daughter in good heart leaves for season (7)
I believe the answer is:
oregano
'leaves for season' is the definition.
(leaves for seasoning)
'lear's daughter in good heart' is the wordplay.
'lear's daughter' becomes 'Regan' (in Shakespeare's King Lear).
'in' indicates putting letters inside.
'heart' means to look at the middle letters.
The central letters of 'good' are 'oo'.
'regan' going into 'oo' is 'OREGANO'.
(Other definitions for oregano that I've seen before include "that's aromatic" , "Dried marjoram" , "herbal preparation" , "leaves for season" , "aromatic plant" .)