Vacuum tube parts (6)
I believe the answer is:
anodes
'vacuum tube parts' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for anodes that I've seen before include "They help current entry" , "Sea don (anag.)" , "Positively charged conductors" , "Positive electrodes" , "Negative terminals of primary cells" .)