Lie about showing true grit (5)
I believe the answer is:
fibre
'true grit' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'lie about' is the wordplay.
'lie' becomes 'fib' (fib is a kind of lie).
'about' becomes 're' (regarding).
'fib'+'re'='FIBRE'
'showing' acts as a link.
Can you help me to learn more?
(Other definitions for fibre that I've seen before include "In brief, a thread" , "Texture - strength of character" , "Dietary material; thread" , "Threadlike substance" , "(Material composed of) thread(s)" .)