Trailer loaded by crew I left (9)
I believe the answer is:
abandoned
'left' is the definition.
(abandoning is a kind of leaving)
'trailer loaded by crew i' is the wordplay.
'trailer' becomes 'ad' (short for advert).
'loaded by' means one lot of letters goes inside another (some letters are loaded into others).
'crew' becomes 'band' (both can mean a group of people).
'i' becomes 'one' (Roman numeral for one).
'band'+'one'='bandone'
'ad' enclosing 'bandone' is 'ABANDONED'.
(Other definitions for abandoned that I've seen before include "Left desolate or empty" , "Derelict, deserted" , "Given up?" , "Left in the lurch, forsaken" , "Quit" .)