The most common and most likely answer to this crossword clue is the 8 letter word HAIRLESS
I've seen this crossword clue in The Sunday Telegraph
H
A
I
R
L
E
S
S
More clues leading to the result HAIRLESS
Buddy explains!

The straight part
We know that "superficially smooth" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case superficially smooth = hairless.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 HAIRLESS mean?
HAIRLESS adjective- Destitute of hair.
- Bald.