Liveliness I found in revolutionary sphere (4)
I believe the answer is:
brio
'liveliness' is the definition.
(thesaurus)
'i found in revolutionary sphere' is the wordplay.
'found in' indicates putting letters inside.
'revolutionary' shows that the letters should be reversed in order.
'sphere' becomes 'orb' (orb is a kind of sphere).
'orb' in reverse letter order is 'bro'.
'i' put within 'bro' is 'BRIO'.
(Other definitions for brio that I've seen before include "Vivacity - spirit" , "Animation (Italian)" , "'Liveliness, vivacity (4)'" , "(Of music) spirit" , "Dash or verve, from Italian" .)