Languid union avoided moving cargo (6)
I believe the answer is:
lading
'cargo' is the definition.
(synonyms)
'languid union avoided moving' is the wordplay.
'union' becomes 'u' (common abbreviation as in 'Trades Union Congress').
'avoided' indicates named letters should be taken away.
'moving' is an anagram indicator.
'languid' with 'u' taken away is 'langid'.
'langid' is an anagram of 'LADING'.
(Other definitions for lading that I've seen before include "Cargo, freight" , "Car engine adjustment" , "Bill of ......; ship's manifest" , "A bill of . . . . . . lists cargo" .)