No end of bother over one mystic (4)
I believe the answer is:
sufi
'mystic' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'no end of bother over one' is the wordplay.
'no end of' means to remove the last letter.
'bother' becomes 'fuss' (synonyms).
'over' says the letters should be written in reverse.
'one' becomes 'I' (Roman numeral).
'fuss' with its final letter taken off is 'fus'.
'fus' reversed gives 'suf'.
'suf'+'i'='SUFI'
Can you help me to learn more?
(Other definitions for sufi that I've seen before include "Muslim inclined to mysticism" , "Muslim mystic" , "Moslem mystic" , "Islamic ascetic" .)