Shortly, choose image (3)
I believe the answer is:
pic
'image' is the definition.
(I've seen this in other clues)
'shortly choose' is the wordplay.
'shortly' means to remove the last letter.
'choose' becomes 'pick' (picking is a kind of choosing).
'pick' with its last letter taken away is 'PIC'.
(Other definitions for pic that I've seen before include "Image (abbr)" , "illustration" , "Photo (colloq.)" , "Photo (informal)" , "Snapshot" .)