Rush in with a stew (5)
I believe the answer is:
haste
'rush' is the definition.
(synonyms)
'in with a stew' is the wordplay.
'in' indicates a hidden word.
'HASTE' is hidden within 'with a stew'.
(Other definitions for haste that I've seen before include "More of this proverbially slows you down" , "Leader abandons modest" , "Speed, hurry" , "Overly eager speed" , "Undue speed" .)