Got upset about the rubbish in a cave (6)
I believe the answer is:
grotto
'a cave' is the definition.
(I know that grotto is a type of cave)
'got upset about the rubbish' is the wordplay.
'upset' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'the rubbish' becomes 'rot' (both can mean nonsense).
'got' with letters rearranged gives 'gto'.
'gto' placed around 'rot' is 'GROTTO'.
'in' is the link.
(Other definitions for grotto that I've seen before include "(Imitation) cave" , "Small cave, perhaps with religious connotations" , "fancy underground area" , "Type of cave, often with religious significance" , "A picturesque cave as in Lourdes (6)" .)