The most common and most likely answer to this crossword clue is the 4 plus 2 plus 5 letter word HARD AS NAILS
H
A
R
D
A
S
N
A
I
L
S
More clues leading to the result HARD AS NAILS
Buddy explains!
The straight part
We know that "How tough could a manicure be?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case how tough could a manicure be? = hard as nails.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.