Part of hand cut on opening of policeman's cuff (5)
I believe the answer is:
thump
'opening of policeman's cuff' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'part of hand cut on' is the wordplay.
'part of' indicates taking the first letters (I've seen 'part' mean this).
'cut' becomes 'tump' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' is an insertion indicator (as in clothing 'on' a person).
The initial letter of 'hand' is 'h'.
'h' placed inside 'tump' is 'THUMP'.
Can you help me to learn more?
(Other definitions for thump that I've seen before include "Hit forcefully" , "Whack" , "Hit hard" , "Pound" , "(Sound of) heavy blow" .)