Crossword Genius

Quickly set off for the outskirts (6)

Ross

I believe the answer is:

presto

I'm a little stuck... Click here to teach me more about this clue!

'quickly' is the definition.
(I've seen this in another clue)

'set off for the outskirts' is the wordplay.
I cannot really see how this works, but
an anagram of 'set' is 'est' which is located in the answer.
'for' could be 'pro' (as in being 'pro' something) and 'pro' is found within the remaining letters.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for presto that I've seen before include "Very fast (mus.)" , "(In music) fast" , "quickly in bars" , "Hey, it's a magician's word" , "Immediately" .)

I've seen this clue in the Evening Standard.
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