Fast Show (7)
I believe the answer is:
express
This clue is a double definition.
'fast' is the first definition.
(I've seen this before)
'show' is the second definition.
(synonyms)
(Other definitions for express that I've seen before include "At high speed like some post" , "Put into words - quick!" , "Squeeze out - speak" , "Put into words - high speed" , "Speak - fast" .)