The most common and most likely answer to this crossword clue is the 9 letter word TWITCHERS
I've seen this crossword clue in The Guardian
T
W
I
T
C
H
E
R
S
More clues leading to the result TWITCHERS
Buddy explains!

The straight part
We know that "They’ll be excited" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they’ll be excited = twitchers.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 TWITCHERS mean?
TWITCHERS noun- Someone or something that twitches.
- An eager birdwatcher who is willing to travel long distances to see rare species. (See the Wikipedia article for origin.)