Rolls filled by kiddies regularly for traveller (5)
I believe the answer is:
rider
'traveller' is the definition.
(rider is a kind of traveller)
'rolls filled by kiddies regularly' is the wordplay.
'rolls' becomes 'RR' (Rolls Royce).
'filled by' means one lot of letters goes inside another.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'kiddies' are 'ide'.
'rr' going around 'ide' is 'RIDER'.
'for' is the link.
(Other definitions for rider that I've seen before include "Jury's recommendation" , "Legal document's additional clause" , "One in the saddle" , "One backing a horse" , "Stipulation" .)