I break speed of sound after ditching ordinary engine (7)
I believe the answer is:
machine
'engine' is the definition.
(I've seen this before)
'i break speed of sound after ditching ordinary' is the wordplay.
'break' means one lot of letters goes inside another (inserted letters break into the word).
'speed of sound' becomes 'mach one' (Mach 1 is the speed of sound).
'after ditching' suggests deleting specific letters.
'ordinary' becomes 'O' (abbreviation e.g. O-Levels).
'machone' with 'o' taken away is 'machne'.
'i' inserted into 'machne' is 'MACHINE'.
(Other definitions for machine that I've seen before include "Contraption" , "Mechanical or electrical device" , "Mechanical apparatus" , "Well-organised and powerful group" , "Powered mechanism" .)