Jerk holding fliers following vehicles (7)
I believe the answer is:
traffic
'vehicles' is the definition.
(I've seen this before)
'jerk holding fliers following' is the wordplay.
'jerk' becomes 'tic' (jerking movement by the body).
'holding' means one lot of letters goes inside another.
'fliers' becomes 'RAF' (Royal Air Force).
'following' becomes 'f' (used when citing page numbers etc).
'raf'+'f'='raff'
'tic' placed around 'raff' is 'TRAFFIC'.
(Other definitions for traffic that I've seen before include "Vehicle flow" , "that may be in jam?" , "What uses road" , "Deals" , "Deal in, trade" .)