Able to pocket second bunch of fives (4)
I believe the answer is:
fist
'bunch of fives' is the definition.
(I've seen this before)
'able to pocket second' is the wordplay.
'able' becomes 'fit' ('fit' can be similar in meaning to 'able').
'to pocket' means one lot of letters goes inside another.
'second' becomes 's' (common abbreviation).
'fit' enclosing 's' is 'FIST'.
(Other definitions for fist that I've seen before include "Bunch of fives" , "Hit with a clenched one" , "Balled hand" , "handwriting?" , "Hand with the fingers clenched in the palm" .)