It causes trouble as an item of luggage (8)
I believe the answer is:
suitcase
'an item of luggage' is the definition.
(I've seen this before)
'it causes trouble' is the wordplay.
'trouble' indicates anagramming the letters.
'it'+'causes'='itcauses'
'itcauses' with letters rearranged gives 'SUITCASE'.
'as' acts as a link.
(Other definitions for suitcase that I've seen before include "Form of luggage" , "one taken on holiday" , "Item of luggage" , "Travelling bag" , "Piece of luggage" .)