Running after light that may be seen through this rock (8)
I believe the answer is:
brighton
'may be seen through this rock' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'running after light' is the wordplay.
'running' becomes 'on' (eg when a machine is running it is on).
'after' says to put letters next to each other.
'light' becomes 'bright' (similar in meaning).
'on' after 'bright' is 'BRIGHTON'.
'that' acts as a link.
Can you help me to learn more?
(Other definitions for brighton that I've seen before include "Where the Prince Regent built his Pavilion" , "seaside location" , "Sussex seaside resort" , "East Sussex resort" , "South coast city combined with Hove" .)