Injure barrier, with time (6)
I believe the answer is:
damage
'injure' is the definition.
(I know that injure is a more specific form of the action damage)
'barrier with time' is the wordplay.
'barrier' becomes 'dam' (dam is a kind of barrier).
'with' means one lot of letters go next to another.
'time' becomes 'age' (an age is a period of time).
'dam'+'age'='DAMAGE'
(Other definitions for damage that I've seen before include "Impair and lower value" , "Detrimental effect" , "destruction" , "Impair, hurt" , "To vandalise" .)