Dry river, land! (6)
I believe the answer is:
secure
'land' is the definition.
(thesaurus)
'dry river' is the wordplay.
'dry' becomes 'sec' ('sec' can be similar in meaning to 'dry').
'river' becomes 'ure' (I have seen 'River of Wensleydale ' mean 'ure' so perhaps 'river' could also mean 'ure').
'sec'+'ure'='SECURE'
(Other definitions for secure that I've seen before include "Safe; fixed" , "Safe and unthreatened" , "Firmly fixed or free from uncertainty" , "Safe and well-protected" , "Firmly in place - free from danger" .)