Ordered the large round power cable (9)
I believe the answer is:
telegraph
'cable' is the definition.
(I know that cable can be written as telegraph)
'ordered the large round power' is the wordplay.
'ordered' indicates an anagram.
'round' means one lot of letters goes inside another.
'power' becomes 'p' (symbol in physics).
'the'+'large'='thelarge'
'thelarge' is an anagram of 'telegrah'.
'telegrah' going around 'p' is 'TELEGRAPH'.
(Other definitions for telegraph that I've seen before include "It's used for communications over wires" , "Device for transmitting information over distance" , "Send message" , "paper" , "A scoreboard" .)