Twitch and begin to wake perhaps (5)
I believe the answer is:
tweak
'twitch' is the definition.
(I know that tweak is a type of twitch)
'begin to wake perhaps' is the wordplay.
'begin' suggests taking the first letters.
'wake perhaps' becomes 'weak' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The first letter of 'to' is 't'.
't'+'weak'='TWEAK'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for tweak that I've seen before include "[TUG]" , "Adjust finely; pinch" , "Make fine adjustments" , "Modify slightly" , "Pinch sharply" .)