Liveliness of one maiden in a race (9)
I believe the answer is:
animation
'liveliness' is the definition.
('animation' can be a synonym of 'liveliness')
'one maiden in a race' is the wordplay.
'one' becomes 'i' (Roman numeral).
'maiden' becomes 'm' (cricket abbreviation).
'in' indicates putting letters inside.
'race' becomes 'nation' (I've seen this before**).
'i'+'m'='im'
'a'+'nation'='anation'
'im' placed within 'anation' is 'ANIMATION'.
'of' acts as a link.
(Other definitions for animation that I've seen before include "Liveliness and vigour" , "Cartoon-making art" , "Liveliness - illusion of movement in cartoon films" , "Liveliness and enthusiasm" , "Cartoon technique" .)