Modernist poet initially bathed in inspiration not to be forgone (4-3)
I believe the answer is:
must-see
'modernist poet initially bathed' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'in inspiration not to be forgone' is the wordplay.
'in' is an insertion indicator.
'inspiration' becomes 'muse' (a muse is someone's inspiration).
'not to be forgone' becomes 'tse' (I am not sure about this - if you are sure you should believe this answer much more).
'muse' placed around 'tse' is 'MUST-SEE'.
Can you help me to learn more?
(Other definitions for must-see that I've seen before include "Remarkable sight" , "Unmissable" .)