Design aircraft, shortly (4)
I believe the answer is:
plan
'design' is the definition.
(synonyms)
'aircraft shortly' is the wordplay.
'aircraft' becomes 'plane' (plane is a kind of aircraft).
'shortly' means to remove the last letter.
'plane' with its last letter removed is 'PLAN'.
(Other definitions for plan that I've seen before include "Project" , "Detailed proposal" , "Map; intention" , "Scale drawing; scheme" , "Road map" .)