Tricky task: sell a pitch (5,4)
I believe the answer is:
sales talk
'pitch' is the definition.
('sales talk' can be a synonym of 'pitch')
'tricky task sell a' is the wordplay.
'tricky' is an anagram indicator.
'task'+'sell'+'a'='tasksella'
'tasksella' is an anagram of 'SALES-TALK'.
(Other definitions for sales talk that I've seen before include "Persuasive material" , "promotional activity" , "Pitch" , "lure to customer" .)