At once (6)
'at once' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for instantly that I've seen before include "With no delay, this very second" , "Immediately, forthwith" , "Without delay or hesitation" .)
(Other definitions for forthwith that I've seen before include "Immediately as with froth" , "Without delay or hesitation" , "without further delay - at which it starts, audibly" , "on the spot" .)
'at once' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for immediately that I've seen before include "Right now" , "Straight away" .)
'at once' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stat that I've seen before include "Photocopy" , "figure used in estimates" , "Might it control warmth" , "copy" , "accepted numerical fact" .)
'at once' is the definition.
(pronto can mean at once or quickly)
This is the entire clue.
(Other definitions for pronto that I've seen before include "Double quick!" , "Promptly, without delay" , "Proton (anag.)" , "Immediately, amigo" , "Quickly, without delay" .)
(Another definition for straight away that I've seen is " Immediately".)