Each dot represents a negative pole (7)
I believe the answer is:
cathode
'a negative pole' is the definition.
(I've seen this in another clue)
'each dot represents' is the wordplay.
'represents' indicates anagramming the letters.
'each'+'dot'='eachdot'
'eachdot' with letters rearranged gives 'CATHODE'.
(Other definitions for cathode that I've seen before include "Positive terminal of a primary cell" , "Ray" , "Battery terminal" , "One's positive" , "Negatively-charged terminal" .)