The most common and most likely answer to this crossword clue is the 7 letter word KINDLED
I've seen this crossword clue in The Times
K
I
N
D
L
E
D
More clues leading to the result KINDLED
Buddy explains!

The straight part
We know that "Fired-up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fired-up = kindled.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 KINDLED mean?
KINDLED verb- To start (a fire) or light (a torch, a match, coals, etc.).
- To arouse or inspire (a passion, etc).
- To begin to grow or take hold.
- (of a rabbit or hare) To bring forth young; to give birth.