Striking a nervous response after short measure (8)
I believe the answer is:
dramatic
'striking' is the definition.
('dramatic' can be a synonym of 'striking')
'a nervous response after short measure' is the wordplay.
'nervous response' becomes 'tic' (I've seen this before).
'after' means one lot of letters go next to another.
'short measure' becomes 'dram'.
'a'+'tic'='atic'
'atic' after 'dram' is 'DRAMATIC'.
(Other definitions for dramatic that I've seen before include "Substantial" , "Like theatre" , "Sudden and striking" , "spectacular" , "Striking, impressive" .)