Measure of spirit before an involuntary spasm’s striking (8)
I believe the answer is:
dramatic
'striking' is the definition.
(I know that striking can be written as dramatic)
'measure of spirit before an involuntary spasm's' is the wordplay.
'measure of spirit' becomes 'dram' (a dram is a small drink of spirits).
'before' says to put letters next to each other.
'an' becomes 'a'.
'involuntary spasm' becomes 'tic' (involuntary bodily movement).
'dram'+'a'+'tic'='DRAMATIC'
(Other definitions for dramatic that I've seen before include "Sudden and striking" , "relating to plays, etc" , "might be staggering" , "Like play" , "spectacular" .)