A little rainfall indicator? (6)
I believe the answer is:
shower
'a little rainfall' is the definition.
'shower' can be an answer for 'rainfall' (shower is a kind of rainfall). I'm not sure about the 'a little' bit.
I can't explain the remainder of the clue.
(Other definitions for shower that I've seen before include "Person uncovering" , "Short fall of rain" , "Something depicting" , "Fall of rain; slack people (slang)" , "One who indicates way" .)