Leave cave altered at interior (6)
I believe the answer is:
vacate
'leave' is the definition.
(to vacate a place is to leave it)
'cave altered at interior' is the wordplay.
'altered' indicates anagramming the letters.
'interior' means one lot of letters goes inside another.
'cave' is an anagram of 'vace'.
'vace' placed around 'at' is 'VACATE'.
(Other definitions for vacate that I've seen before include "Leave behind empty" , "Leave (a place previously occupied)" , "Make empty" , "Leave (a position)" , "Depart from, leave empty" .)