Hurdler say in line runs in stockings (9)
I believe the answer is:
racehorse
'hurdler say' is the definition.
(a racehorse might jump hurdles)
'line runs in stockings' is the wordplay.
'line' becomes 'race' (a line or race of people).
'runs' becomes 'r' (cricket abbreviation).
'in' is an insertion indicator.
'stockings' becomes 'hose' (I've seen this in other clues).
'r' placed inside 'hose' is 'horse'.
'race'+'horse'='RACEHORSE'
'in' acts as a link.
(Other definitions for racehorse that I've seen before include "Which a jockey rides" , "Arab possibly" , "hope for better?" , "Animal" , "jumper?" .)