Is able to get a long lead into the duct (5)
I believe the answer is:
canal
'the duct' is the definition.
(synonyms)
'is able to get a long lead' is the wordplay.
'is able to' becomes 'can' (if you can do something you are able to do it).
'get' means one lot of letters go next to another.
'lead' says to take the initial letters.
The initial letter of 'long' is 'l'.
'can'+'a'+'l'='CANAL'
'into' acts as a link.
(Other definitions for canal that I've seen before include "Man-made watercourse" , "Man-made strip of water" , "eg Grand Union" , "Manmade flower" , "Man-made waterway" .)