From fish, a stench — move fast! (6)
I believe the answer is:
hasten
'move fast' is the definition.
'from fish a stench' is the wordplay.
'from' indicates a hidden word.
'HASTEN' can be found hidden inside 'fish a stench'.
(Other definitions for hasten that I've seen before include "Hurry up in old-fashioned way" , "Make faster" , "Act or move fast" , "Travel with expedition" , "Rush" .)