Great help unravelling wire (9)
I believe the answer is:
telegraph
'wire' is the definition.
(telegraph wire is a kind of wire)
'great help unravelling' is the wordplay.
'unravelling' indicates an anagram.
'great'+'help'='greathelp'
'greathelp' is an anagram of 'TELEGRAPH'.
(Other definitions for telegraph that I've seen before include "It's used for communications over wires" , "Send message" , "Electrical transmission of coded signals" , "Device for transmitting information over distance" , "Daily" .)