Talk of flogging tar after beer stashed in ship (5,5)
I believe the answer is:
sales pitch
'talk of flogging' is the definition.
(I've seen this before)
'tar after beer stashed in ship' is the wordplay.
'tar' becomes 'pitch' (synonyms).
'after' means one lot of letters go next to another.
'beer' becomes 'ale' (type of beer).
'stashed in' is an insertion indicator.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'ale' going into 'ss' is 'sales'.
'pitch' after 'sales' is 'SALES PITCH'.
(Other definitions for sales pitch that I've seen before include "Spiel; patter" , "Market stall" , "that's delivered by rep" , "Sharks can be seen on this" , "talk of flogging" .)