Light close to central current unit (4)
I believe the answer is:
lamp
'light' is the definition.
(lamp is a kind of light)
'close to central current unit' is the wordplay.
'close to' indicates one should take the final letters (the 'close' to the word).
'current unit' becomes 'amp' (amp is a kind of current unit).
The last letter of 'central' is 'l'.
'l'+'amp'='LAMP'
(Other definitions for lamp that I've seen before include "Florence Nightingale was the Lady with the . . . ." , "Artificial source of illumination" , "Source of light, usually portable" , "Device providing illumination" , "Appliance producing light" .)