Pass out with many a twitch (5)
I believe the answer is:
spasm
'a twitch' is the definition.
(I've seen this before)
'pass out with many' is the wordplay.
'out with' indicates an anagram (out can mean wrong or inaccurate).
'many' becomes 'm'.
'pass' anagrammed with 'm' can make 'SPASM'.
(Other definitions for spasm that I've seen before include "Involuntary muscular contraction" , "Involuntary contraction of muscles" , "Tic, sudden contraction" , "sudden movement" , "Sudden involuntary contraction of a muscle" .)