Glint half seen flickering in the evening (9)
I believe the answer is:
nightfall
'the evening' is the definition.
(thesaurus)
'glint half seen flickering' is the wordplay.
'seen flickering' indicates an anagram.
'glint'+'half'='glinthalf'
'glinthalf' anagrammed gives 'NIGHTFALL'.
'in' acts as a link.
(Other definitions for nightfall that I've seen before include "after sunset" , "gloaming" , "when evenings draw in" , "Dusk" , "when visibility reduces" .)