Last traces of excess rain creep along and drop off (6)
I believe the answer is:
snooze
'drop off' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for snooze that I've seen before include "Forty winks" , "Take a nap" , "Quick nap" , "Sleep lightly" , "A brief nap" .)