Feeble end of bulletin in suitable thread (8)
I believe the answer is:
filament
'thread' is the definition.
(I have seen 'Thin thread ' mean 'filament' so perhaps 'thread' could also mean 'filament')
'feeble end of bulletin in suitable' is the wordplay.
'feeble' becomes 'lame' (synonyms).
'end of' says to take the final letters.
'in' is an insertion indicator.
'suitable' becomes 'fit' (similar in meaning).
The final letter of 'bulletin' is 'n'.
'lame'+'n'='lamen'
'lamen' put into 'fit' is 'FILAMENT'.
(Other definitions for filament that I've seen before include "Slender thread - conducting wire" , "Thin thread (e.g. in bulb)" , "Part of light" , "'Thin wire, in a bulb say (8)'" , "Slender fibre or wire" .)