Speak fast (7)
I believe the answer is:
express
I believe this clue is a double definition.
'speak' is the first definition.
(I've seen this before)
'fast' is the second definition.
(I've seen this before)
(Other definitions for express that I've seen before include "Convey; particular; train" , "special delivery" , "Utter - non-stop" , "Speak - fast" , "Train; utter" .)