Wake from sleep — plan to introduce oxygen (5)
I believe the answer is:
rouse
'wake from sleep' is the definition.
(I've seen this in another clue)
'plan to introduce oxygen' is the wordplay.
I cannot really see how this works, but
'oxygen' could be 'o' (atomic symbol for oxygen) and 'o' is found in the answer.
'plan' could be 'ruse' (I have seen 'Cunning plan' mean 'ruse' so perhaps 'plan' could also mean 'ruse') and 'ruse' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rouse that I've seen before include "Waken" , "Wake up, make active" , "Cause to wake up and come alert" , "To start" , "Bring out of sleep" .)