Delivery of a herbal extract to a northern city (6)
I believe the answer is:
yorker
'delivery' is the definition.
(type of cricket delivery)
'herbal extract to a northern city' is the wordplay.
'herbal extract' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to a' is a charade indicator (letters next to each other) (I've seen this in other clues).
'northern city' becomes 'york' (I've seen this before).
'er' put after 'york' is 'YORKER'.
'of a' is the link.
Can you help me to learn more?
(Other definitions for yorker that I've seen before include "Delivery pitching directly under the bat" , "Cricket delivery, pitching under the bat" , "Bowler's delivery type" , "Cricket delivery aimed at the feet" , "Type of cricket delivery" .)