Graduate goes back to replace lid of glossy substance which will put an end to it (7)
I believe the answer is:
abolish
'end to it' is the definition.
'abolish' can be an answer for 'end' (I've seen this in another clue). I'm not certain of the 'to it' bit.
'graduate goes back to replace lid of glossy substance which will put an' is the wordplay.
I cannot really understand how this works, but
'of' could be 'o' and 'o' is located in the answer.
'substance' could be 'li' (Li is an example) and 'li' is located in the answer.
'an' could be 'a' and 'a' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abolish that I've seen before include "Drop" , "Formally do away with" , "Put an end to, cancel" , "Put an end to (custom)" , "Put an end to, formally" .)