Little Simz regularly ahead of everybody (5)
I believe the answer is:
small
'little' is the definition.
(I know that little can be written as small)
'simz regularly ahead of everybody' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'ahead of' says to put letters next to each other (some letters go in front of others).
'everybody' becomes 'all' (all people).
The alternate letters of 'simz' are 'sm'.
'sm'+'all'='SMALL'
(Other definitions for small that I've seen before include "Unimportant; young" , "Undersized" , "tiddly" , "Insignificant; young" , "Lower middle of the back" .)