Tremor seldom displays a bit (6)
I believe the answer is:
morsel
'a bit' is the definition.
('morsel' can be a synonym of 'bit')
'tremor seldom displays' is the wordplay.
'displays' indicates the answer is hidden within the clue.
'MORSEL' is hidden in the letters of 'tremor seldom'.
(Other definitions for morsel that I've seen before include "Bite to eat" , "A scrap or shred of food" , "Part" , "(Tasty) bit" , "A shred as of bread" .)