One's abusing no end of that dope? (7)
I believe the answer is:
pothead
'one's' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'abusing no end of that dope?' is the wordplay.
'abusing' is an anagram indicator (I've seen 'abused' mean this).
'no end of' means to remove the last letter.
'that' with its final letter taken off is 'tha'.
'tha'+'dope'='thadope'
'thadope' anagrammed gives 'POTHEAD'.
Can you help me to learn more?
(Other definitions for pothead that I've seen before include "Drug addict" , "One who uses dope" .)