The most common and most likely answer to this crossword clue is the 6 letter word BIONIC
I've seen this crossword clue in The Guardian
B
I
O
N
I
C
More clues leading to the result BIONIC
- Like Steve Austin on island cornered by writer
- British couple carrying on about superhuman
- Superhuman bloke is often needed in crisis initially
- Artificially boosted babies’ hearts with functioning circuit
- Superhuman bishop, a particular sort of Greek
- Bishop with classic order having non-human features?
- Somehow artificial bishop having a certain Greek style
- 12a
Buddy explains!

The straight part
We know that "superhuman" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case superhuman = bionic.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 BIONIC mean?
BIONIC adjective- Related to bionics.
- Of a biological organism, having been enhanced by electronic or mechanical parts; cyborg.
- Superhuman