Nearby fellow enthralled by remarkable evening (9)
I believe the answer is:
nightfall
'evening' is the definition.
(I've seen this before)
'nearby fellow enthralled by remarkable' is the wordplay.
'nearby' becomes 'nigh' (I've seen this before).
'fellow' becomes 'f' (abbreviation - of a society etc.).
'enthralled by' means one lot of letters goes inside another ('enthral' can mean 'capture').
'remarkable' becomes 'tall' (I've seen this before).
'f' going within 'tall' is 'tfall'.
'nigh'+'tfall'='NIGHTFALL'
(Other definitions for nightfall that I've seen before include "gloaming" , "when the light fails" , "start of the dark time" , "Dusk" , "Arrival of darkness" .)