The most common and most likely answer to this crossword clue is the 7 letter word DEATHLY
D
E
A
T
H
L
Y
Buddy explains!

The straight part
We know that "so very pale" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case so very pale = deathly.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 DEATHLY mean?
DEATHLY adjective- Appearing as though dead, or on the verge of death.
- Deadly, fatal, causing death.
- Extreme.
- In a way that resembles death.
- Extremely, dreadfully.