Not only don't come but prevent others coming (4,4)
I believe the answer is:
keep away
'not only don't' is the definition.
The definition suggests a verb in its base form which matches the answer.
'come but prevent others coming' is the wordplay.
I cannot really see how this works, but
'prevent' could be 'keep' (synonyms) and 'keep' is located in the answer.
The remaining letters 'away' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for keep away that I've seen before include "Don't come near" , "Remain at a distance" .)