Start to go (3)
I believe the answer is:
gee
'start to go' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gee that I've seen before include "Mild expression of surprise, may go before whiz" , "G" , "Mild exclamation" , "move faster" , "provided by substitute for ginger?" .)