Long narrow flag taken from brook with hesitation (8)
I believe the answer is:
streamer
'long narrow flag' is the definition.
(I've seen this before)
'brook with hesitation' is the wordplay.
'brook' becomes 'stream' (I've seen this in another clue).
'with' is a charade indicator (letters next to each other).
'hesitation' becomes 'er' (sound used when hesitating).
'stream'+'er'='STREAMER'
'taken from' acts as a link.
(Other definitions for streamer that I've seen before include "Arrest me carrying floating ribbon" , "Long flag, tapering perhaps" , "Long decorative strip of material" , "Bit of bunting" , "Long narrow ribbon for er, master" .)