The most common and most likely answer to this crossword clue is the 12 letter word THUNDERBIRDS
T
H
U
N
D
E
R
B
I
R
D
S
Buddy explains!
The straight part
We know that "TV series" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tv series = thunderbirds.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 THUNDERBIRDS mean?
THUNDERBIRDS noun- A mythological bird, often associated with stormy weather, especially in various indigenous North American mythologies.
- An Australian insectivorous songbird (Pachycephala pectoralis, formerly Pachycephala gutturalis), whose male is conspicuously marked with black and yellow, and has a black crescent on the breast.