Metaphysical poet, endlessly astonishing person (6)
I believe the answer is:
marvel
'astonishing person' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'metaphysical poet endlessly' is the wordplay.
'metaphysical' becomes 'm' (this might be a standard abbreviation which I don't know about).
'poet' becomes 'marvell' (m7th-century poet Andrew Marvell).
'endlessly' says to take the centre (the ends of the words are removed).
The central letters of 'marvell' are 'arvel'.
'm'+'arvel'='MARVEL'
Can you help me to learn more?
(Other definitions for marvel that I've seen before include "Wonderful thing/person" , "Feel sense of wonder and awe" , "Amazing person or event" , "Wonder at, be amazed" , "Express astonishment" .)