Relieve from aridity (3)
I believe the answer is:
rid
'relieve' is the definition.
(I know that relieve is a kind of rid)
'from aridity' is the wordplay.
'from' says the answer is hidden in the clue.
'RID' is hidden in the letters of 'aridity'.
(Other definitions for rid that I've seen before include "Lose, shake off" , "Free, disencumber" , "Free from something unpleasant" , "Free (someone of something unwanted)" , "Free, deliver, clear" .)