Got rot treated in the cave (6)
I believe the answer is:
grotto
'the cave' is the definition.
(grotto is a kind of cave)
'got rot treated' is the wordplay.
'treated' is an anagram indicator.
'got'+'rot'='gotrot'
'gotrot' is an anagram of 'GROTTO'.
'in' acts as a link.
(Other definitions for grotto that I've seen before include "It's left on Dec 24 by Santa and his reindeer" , "Small cave, perhaps with religious connotations" , "Fancy cave" , "Small cave as at Lourdes" , "Artificially or naturally ornamented cave" .)