Very unreliable engine outside in dusk (7)
I believe the answer is:
evening
'dusk' is the definition.
(I've seen this before)
'very unreliable engine outside' is the wordplay.
'very' becomes 'v' (abbreviation).
'unreliable' indicates anagramming the letters.
'outside' means one lot of letters goes inside another.
'engine' is an anagram of 'eening'.
'v' placed into 'eening' is 'EVENING'.
'in' acts as a link.
(Other definitions for evening that I've seen before include "Late afternoon" , "Balancing" , "Preparing flat" , "Making flat" , "Dusk" .)