Rescue from deep river, swimming out of depth (8)
I believe the answer is:
reprieve
'rescue' is the definition.
(reprieve is a kind of rescue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for reprieve that I've seen before include "Let off; brief respite" , "Postponement of punishment" , "Let off punishment" , "Delay or cancel punishment" , "Temporary relief from harm" .)