Keep in a good state of repair (8)
I believe the answer is:
maintain
'keep in a good state of repair' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for maintain that I've seen before include "Keep in safety and protect from harm and decay" , "Keep in a good state of repair" , "Keep in good order" , "Preserve or contend" , "Keep in existence or in repair" .)