Twitch at first to wake in confusion (5)
I believe the answer is:
tweak
'twitch' is the definition.
(thesaurus)
'first to wake in confusion' is the wordplay.
'first' indicates taking the first letters.
'in confusion' indicates anagramming the letters.
The first letter of 'to' is 't'.
'wake' is an anagram of 'weak'.
't'+'weak'='TWEAK'
'at' is the link.
(Other definitions for tweak that I've seen before include "Slightly alter" , "Improve (something) by fine adjustments" , "Twist; adjust finely" , "Modify slightly" , "Slightly shift" .)