Liveliness of tailless monkey (5)
I believe the answer is:
verve
'liveliness' is the definition.
(verve is a kind of liveliness)
'tailless monkey' is the wordplay.
'tailless' means to remove the last letter.
'monkey' becomes 'vervet' (vervet is a kind of monkey).
'vervet' with its last letter removed is 'VERVE'.
'of' is the link.
(Other definitions for verve that I've seen before include "Energy and zest" , "Gusto; energy" , "zip" , "Sparkling enthusiasm" , "Vigour, spirit, style" .)