The most common and most likely answer to this crossword clue is the 8 letter word INGUINAL
I've seen this crossword clue in The Guardian
I
N
G
U
I
N
A
L
More clues leading to the result INGUINAL
Buddy explains!

The straight part
We know that "in the groin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in the groin = inguinal.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.
Crossword Answer definitions
INGUINAL adjective- Of or pertaining to the groin.