After losing son, chap's empty (4)
I believe the answer is:
bail
'after losing son chap's' is the definition.
'Bail' can be an answer for 'chap's'. I am not sure about the 'after losing son' bit.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bail that I've seen before include "Piece placed on top of cricket stumps" , "Cross piece on wicket" , "Security for release from custody" , "One of two on the stumps" , "Temporary release of an accused person on conditions" .)