Bring dope on to assemble a temporary crossing (7,6)
I believe the answer is:
pontoon bridge
'a temporary crossing' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'bring dope on to assemble' is the wordplay.
'assemble' is an anagram indicator.
'bring'+'dope'+'on'+'to'='bringdopeonto'
'bringdopeonto' anagrammed gives 'PONTOON-BRIDGE'.
Can you help me to learn more?
(Other definitions for pontoon bridge that I've seen before include "Floating structure for crossing water" , "River crossing on floating supports" , "channel crossing" , "Makeshift way to get over current" , "A large float passing between banks" .)