Bottle just about right to be knocked back? (5)
I believe the answer is:
nerve
'bottle' is the definition.
(both can mean courage)
'just about right to be knocked back?' is the wordplay.
'just' becomes 'even'.
'about' indicates putting letters inside.
'right' becomes 'r' (common abbreviation).
'to be knocked back?' says the letters should be written in reverse (I've seen 'knock back' mean this).
'even' enclosing 'r' is 'evren'.
'evren' back-to-front is 'NERVE'.
(Other definitions for nerve that I've seen before include "Courage, coolness in danger" , "Cheek; self-possession" , "Strand of body fibre" , "Bodily fibre that transmits sensations" , "Bundle of fibres < in face" .)