Lured over hard first barrier (6)
I believe the answer is:
hurdle
'barrier' is the definition.
(hurdle is a kind of barrier)
'lured over hard first' is the wordplay.
'over' is an anagram indicator.
'hard' becomes 'h' (**).
'first' means one lot of letters go next to another.
'lured' with letters rearranged gives 'urdle'.
'urdle' after 'h' is 'HURDLE'.
(Other definitions for hurdle that I've seen before include "Light movable barrier in certain races" , "Challenge (to be cleared)" , "Barrier (to be jumped)" , "Obstacle (that needs to be overcome)" , "Vault" .)