Shorten key flyover (7)
I believe the answer is:
abridge
'shorten' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for abridge that I've seen before include "trim" , "Edit down" , "Shorten for e.g. radio" , "Shorten by using fewer words" , "Cut short" .)