Boss sacked cries (4)
I believe the answer is:
sobs
'cries' is the definition.
(sobbing is a kind of crying)
'boss sacked' is the wordplay.
'sacked' indicates anagramming the letters.
'boss' with letters rearranged gives 'SOBS'.
(Other definitions for sobs that I've seen before include "Cries loudly" , "Weeps heavily for boss" , "Weeps heavily (4)" , "cries uncontrollably" , "Weeps audibly" .)