Boo-hoo
I believe the answer is:
sob
'boo-hoo' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sob that I've seen before include "Snivel" , "Cry noisily" , "Weep heavily, wail" , "Cry bitterly" , "Weep noisily" .)