Talk about singular herb (7)
I believe the answer is:
parsley
'herb' is the definition.
(I know that parsley is a type of herb)
'talk about singular' is the wordplay.
'talk' becomes 'parley' (to parley is to talk with an enemy).
'about' indicates putting letters inside.
'singular' becomes 's' (abbreviation in grammar).
'parley' going around 's' is 'PARSLEY'.
(Other definitions for parsley that I've seen before include "Herb with either flat or crinkly leaves" , "Culinary herb" , "You might misuse this herb sparely" , "Herbal garnish" , "Herb (flat-leafed or curly)" .)