Old monk, drunk, means well in the end (6)
I believe the answer is:
anselm
'old monk' is the definition.
The definition suggests a singular noun which matches the answer.
'drunk means well in the end' is the wordplay.
'drunk' is an anagram indicator.
'in the end' says to take the final letters.
The final letter of 'well' is 'l'.
'means'+'l'='meansl'
'meansl' with letters rearranged gives 'ANSELM'.
Can you help me to learn more?
(Other definitions for anselm that I've seen before include "Italian monk, saint and Archbishop of Canterbury, 1093-1109" , "Saintly archbishop" , "Man" , "Sainted Archbishop of Canterbury" , "Christian saint" .)