A chap I restrained with great force (5)
I believe the answer is:
amain
'with great force' is the definition.
(I've seen this in another clue)
'a chap i restrained' is the wordplay.
'a chap' becomes 'aman' (I am not sure about this - if you are sure you should believe this answer much more).
'restrained' is an insertion indicator (inserted letters are restrained by others).
'aman' going around 'i' is 'AMAIN'.
Can you help me to learn more?
(Other definitions for amain that I've seen before include "violently" , "showing great strength in poetry" , "force" , "at full speed" , "at great speed" .)