Harass chap with stick, initially (6)
I believe the answer is:
pester
'harass' is the definition.
(I know that pester is a type of torment)
'chap with stick initially' is the wordplay.
'chap' becomes 'Peter' (Peter is a man's name).
'with' indicates putting letters inside.
'stick initially' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'peter' placed around 's' is 'PESTER'.
Can you help me to learn more?
(Other definitions for pester that I've seen before include "Bug" , "Annoy with frequent questions" , "Annoy persistently" , "Nag, badger" , "Annoy with frequent requests" .)