Low on rainfall (4)
I believe the answer is:
arid
'low on rainfall' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arid that I've seen before include "(Of an area) very dry" , "Without water" , "Dry, devoid of interest" , "(Of land) very dry" , "Parched and barren" .)