Dry river saved by charity (4)
I believe the answer is:
arid
'dry' is the definition.
(similar in meaning)
'river saved by charity' is the wordplay.
'river' becomes 'r'.
'saved by' means one lot of letters goes inside another (I've seen this in other clues).
'charity' becomes 'aid' (I've seen this before).
'r' put into 'aid' is 'ARID'.
(Other definitions for arid that I've seen before include "Sterile" , "Dry raid" , "Excessively dry" , "Parched with heat" , "Drought-hit" .)