The most common and most likely answer to this crossword clue is the 8 letter word CACTUSES
C
A
C
T
U
S
E
S
More clues leading to the result CACTUSES
Buddy explains!

The straight part
We know that "sources of big pricks" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sources of big pricks = cactuses.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 CACTUSES mean?
CACTUSES noun- Any member of the family Cactaceae, a family of flowering New World succulent plants suited to a hot, semi-desert climate.
- Any succulent plant with a thick fleshy stem bearing spines but no leaves, such as euphorbs.