Trucking rig (4)
I believe the answer is:
semi
'trucking rig' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for semi that I've seen before include "match, the last but one?" , "Type of house (UK) - type of truck (US)" , "Style of house" , "Property attached to another" , "Not quite the biggest tie" .)