Crossword Genius

Bag rocketing as at speed of light (3)

Ross

I believe the answer is:

sac

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

'bag' is the definition.
(a small bag)

'rocketing as at speed of light' is the wordplay.
'rocketing as' becomes 'sa' (I can't justify this - if you can you should believe this answer much more).
'at' is a charade indicator (letters next to each other).
'speed of light' becomes 'c' (I've seen this in other clues).
'sa'+'c'='SAC'

Can you help me to learn more?

(Other definitions for sac that I've seen before include "Bladder" , "Distended membrane; pouch-like cavity" , "Traditional entitlement to hold court" , "Bag-like cavity" , "Bag, pouch; cyst" .)

I've seen this clue in The Sun.
Want a hint initially instead of a full solution? Install my app