Unimpaired; whole (6)
I believe the answer is:
intact
This clue is a double definition.
'unimpaired' is the first definition.
(similar in meaning)
'whole' is the second definition.
(similar in meaning)
(Other definitions for intact that I've seen before include "Whole and complete" , "Inviolate" , "Entire and whole" , "Complete - unbroken" , "Not damaged or missing a part" .)