A drop in the rate, maybe (4)
I believe the answer is:
tear
'a drop' is the definition.
(teardrop)
'rate maybe' is the wordplay.
'maybe' indicates anagramming the letters.
'rate' is an anagram of 'TEAR'.
'in the' acts as a link.
(Other definitions for tear that I've seen before include "Droplet; rip" , "A rip and a sign of sadness" , "speed" , "Shred" , "Rent - drop" .)