Saw tonne being transported (5)
I believe the answer is:
tenon
'saw' is the definition.
(I've seen this before)
'tonne being transported' is the wordplay.
'being transported' indicates an anagram.
'tonne' is an anagram of 'TENON'.
(Other definitions for tenon that I've seen before include "Wooden projection shaped to fit in a mortise joint" , "Type of hacksaw" , "Mortise extension" , "piece of carpentry?" , "Join" .)