The most common and most likely answer to this crossword clue is the 5 letter word FIBRE
I've seen this crossword clue in The Daily Telegraph
F
I
B
R
E
More clues leading to the result FIBRE
- Basic material to lie on
- Lie about moral strength
- In sack, black thread
- Lie about what keeps me going regularly
- Material being initially engulfed in flames
- Lie on wool for one
- Thread starts to burn in the flames
- Lie about one’s dietary requirement
- Make false claim about healthy food
- Bishop wears light make-up
Buddy explains!

The straight part
We know that "strength of character" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case strength of character = fibre.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 FIBRE mean?
FIBRE noun- A single piece of a given material, elongated and roughly round in cross-section, often twisted with other fibres to form thread.
- Material in the form of fibres.
- Dietary fibre.
- Moral strength and resolve.
- The preimage of a given point in the range of a map.
- Said to be of a morphism over a global element: The pullback of the said morphism along the said global element.
- A kind of lightweight thread of execution.
- A long tubular cell found in muscle tissue; myocyte.