Engine to drive Jack over Egypt on vacation (6)
I believe the answer is:
ramjet
'engine' is the definition.
(I know that ramjet is a type of jet engine)
'drive jack over egypt on vacation' is the wordplay.
'drive' becomes 'ram' (RAM drive on a computer).
'jack' becomes 'J' (playing card abbreviation).
'over' is a charade indicator (letters next to each other).
'on vacation' says to hollow out the word (remove centre letters) (after the inside letters have vacated the word).
'egypt' with its middle removed is 'et'.
'ram'+'j'+'et'='RAMJET'
'to' acts as a link.
(Other definitions for ramjet that I've seen before include "starter engine" , "Type of aircraft engine" , "Type of air engine" , "Type of aero-engine" .)