Fast, say (7)
I believe the answer is:
express
I believe this clue is a double definition.
'fast' is the first definition.
(I've seen this before)
'say' is the second definition.
(to express something is to say it)
(Other definitions for express that I've seen before include "Fast train; specific" , "Transport" , "Quick -- exact" , "Verbalise - very fast" , "Articulate, give voice to" .)