Pastor encourages English weed (9,5)
I believe the answer is:
shepherds purse
'weed' is the definition.
(plant which may be considered a weed)
'pastor encourages english' is the wordplay.
'pastor' becomes 'shepherd' (pastor literally means shepherd).
'encourages' becomes 'spurs' (spurring is a kind of encouraging).
'english' becomes 'e' (abbreviation).
'shepherd'+'spurs'+'e'='SHEPHERDS PURSE'
(Other definitions for shepherds purse that I've seen before include "Herb" , "weed" .)