Prevents from drifting into open spaces (5)
I believe the answer is:
moors
'open spaces' is the definition.
Although both the answer and definition are verbs in their -s form, I don't see how they can define each other.
'prevents from drifting' is the wordplay.
I cannot quite understand how this works, but
'from' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
The remaining letters 'mors' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'into' is the link.
Can you help me to learn more?
(Other definitions for moors that I've seen before include "Berths" , "wild areas" , "Ties up a boat" , "Open heathlands" , "Conquerors once" .)