The most common and most likely answer to this crossword clue is the 7 letter word SIEMENS
I've seen this crossword clue in The Daily Telegraph
S
I
E
M
E
N
S
More clues leading to the result SIEMENS
Buddy explains!

The straight part
We know that "Electrical units" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case electrical units = siemens.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SIEMENS mean?
SIEMENS noun- In the International System of Units, the derived unit of electrical conductance; the electric conductance in a body that has a resistance of one ohm. Symbol: S