Excursion getting away in the middle of the night (6)
I believe the answer is:
outing
'excursion' is the definition.
('outing' can be a synonym of 'excursion')
'away in the middle of the night' is the wordplay.
'away' becomes 'out' ('out' can be a synonym of 'away'**).
'the middle of' means to look at the middle letters.
The middle letter of 'night' is 'g'.
'out'+'in'+'g'='OUTING'
'getting' acts as a link.
(Other definitions for outing that I've seen before include "Day trip" , "Short pleasure trip" , "Day excursion" , "Excursion, trip" , "Revealing orientation" .)