Sign of sobbing at different rate (4)
I believe the answer is:
tear
'sign of sobbing' is the definition.
'tear' can be an answer for 'sobbing' (thesaurus). I'm not certain of the 'sign of' bit.
'different rate' is the wordplay.
'different' indicates anagramming the letters (letters placed in a different order).
'rate' with letters rearranged gives 'TEAR'.
'at' is the link.
Can you help me to learn more?
(Other definitions for tear that I've seen before include "Rush - to pull apart" , "Rip, pull apart" , "Small globule of sorrow" , "Hurry" , "Drop secreted by the lacrimal glands" .)