Rocky lump is boundary by which there is old ceremony (9)
I believe the answer is:
meteorite
'rocky lump' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'boundary by which there is old ceremony' is the wordplay.
I cannot quite understand how this works, but
'boundary' could be 'mete' (I've seen this in another clue) and 'mete' is located in the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is present in the answer.
'ceremony' could be 'rite' (rite is a kind of ceremony) and 'rite' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'is' is the link.
Can you help me to learn more?
(Other definitions for meteorite that I've seen before include "Piece of rock fallen from outer space" , "fallen stone" , "Something falling from the sky" , "Lump from space" , "Matter in the solar system that reaches earth" .)