Burst of train speed unexciting (10)
I believe the answer is:
pedestrian
'unexciting' is the definition.
(I've seen this before)
'burst of train speed' is the wordplay.
'burst of' indicates anagramming the letters (I've seen 'bursts' mean this).
'train'+'speed'='trainspeed'
'trainspeed' is an anagram of 'PEDESTRIAN'.
(Other definitions for pedestrian that I've seen before include "Run-of-the mill" , "footman" , "Hiker" , "A person travelling on foot" , "Walker; prosaic" .)