The most common and most likely answer to this crossword clue is the 8 letter word UNCOMBED
U
N
C
O
M
B
E
D
Buddy explains!
The straight part
We know that "in need of a groom" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in need of a groom = uncombed.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 UNCOMBED mean?
UNCOMBED verb- To reverse the effect of combing; to muss.
- To remove a backcomb from.
- To comb out; to disentangle.
- Not combed.