Ruined boss cries (4)
I believe the answer is:
sobs
'cries' is the definition.
(sobbing is a kind of crying)
'ruined boss' is the wordplay.
'ruined' indicates anagramming the letters.
'boss' anagrammed gives 'SOBS'.
(Other definitions for sobs that I've seen before include "cries uncontrollably" , "Is unhappy" , "convulsions" , "Weeps noisily" , "Given evidence of distress" .)